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Intervention: Let's Begin with the Letter People®
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Appendices


Appendix A1.1 Study characteristics: Preschool Curriculum Evaluation Research Consortium, 2008 (randomized controlled trial)

Characteristic Description
Study citation

Preschool Curriculum Evaluation Research (PCER) Consortium. (2008). Doors to Discovery and Let’s Begin with the Letter People. In Effects of preschool curriculum programs on school readiness (pp. 85–98). Washington, DC: National Center for Education Research, Institute of Education Sciences, U.S. Department of Education.
Participants The study, conducted during the 2003–04 and 2004–05 school years, included two intervention groups (Let’s Begin with the Letter People® and Doors to Discovery™) and a control group. Nineteen full-day Head Start and public prekindergarten preschools were recruited for the study. From these 19 preschools, 95 teachers/classrooms were recruited, of which 76 were included in random assignment. The researchers randomly assigned the 19 preschools to three treatment conditions (Let’s Begin with the Letter People®, Doors to Discovery™, and control) with all classrooms within a preschool being assigned to the same treatment condition. The resulting sample of teachers/classrooms included 24 Let’s Begin with the Letter People® classrooms, 25 Doors to Discovery™ classrooms, and 27 control classrooms. Forty-five of the 76 classrooms were then randomly selected to participate in the PCER study. One of the 45 classrooms dropped out, leaving 15 Let’s Begin with the Letter People®, 14 Doors to Discovery™, and 15 control classrooms. Seven children (whose parents had provided consent to participate in the study) were randomly selected from each classroom for a total of 308 children. The parental consent rate was 65% for the treatment group (combined Let’s Begin with the Letter People® and Doors to Discovery™) and 55% for the control group. The total number of participating children in the study at baseline was 297 (100 Let’s Begin with the Letter People®, 101 Doors to Discovery™, and 96 control). At baseline, children in the study averaged 4.6 years of age; 55% were male; and 43% were Hispanic, 30% were white, and 13% were African-American. The analysis sample for the Let’s Begin with the Letter People® study included 184 children (95 Let’s Begin with the Letter People® and 89 control). Depending on the outcome, child-level attrition ranged from 6% to 7%.
Setting The Let’s Begin with the Letter People® study was conducted with children in 19 preschools in Houston, Texas. The sample included 30 Head Start and public prekindergarten (Title I and non-Title I) classrooms (15 Let’s Begin with the Letter People® and 15 control).
Intervention Let’s Begin with the Letter People® is a comprehensive prekindergarten curriculum that is organized thematically. Literacy learning is integrated across topic areas, including science, health and safety, art, math, spatial concepts, and music, as well as development of large and small motor skills. The curriculum focuses on literacy and language skills, including oral language, phonological and phonemic awareness, and letter knowledge. The curriculum lessons address the development of letter knowledge in various contexts (for example, circle time, small group, large group) and activities (for example, center activities, story times). Classroom practices include teacher-directed activities, application of skills, and independent practice with activities that are tied to the curriculum. The Let’s Begin with the Letter People® classroom includes interest centers (for example, Paint Corner, Blocks, Drama Center, Mathematics). Curriculum materials include Letter People Huggables®. Each Letter Person represents a letter of the alphabet and has distinguishing characteristics that are readily associated with the sound represented by the letter. Each classroom’s fidelity to the curriculum was rated on a four-point scale ranging from “not at all” (0) to “high” (3). The average score for Let’s Begin with the Letter People® classrooms was 1.86 on this measure.
Comparison Business-as-usual using teacher-developed, nonspecific curricula. Control teachers’ classrooms were rated with the same fidelity measure used in the Let’s Begin with the Letter People® classrooms, which ranged from 0 to 3. The average score for the control classrooms using this measure was 1.0.
Primary outcomes and measurement The outcome domains assessed were children’s oral language, print knowledge, phonological processing, and math. Oral language was assessed with the Peabody Picture Vocabulary Test–III (PPVT-III) and the Test of Language Development–Primary: III (TOLD-P:3) Grammatic Understanding subtest. Print knowledge was assessed with the Test of Early Reading Ability–III (TERA-3), the Woodcock-Johnson–III (WJ-III) Letter-Word Identification subtest, and the WJ-III Spelling subtest. Phonological processing was assessed with the Preschool Comprehensive Test of Phonological and Print Processing (Pre-CTOPPP) Elision subtest. Math was assessed with the WJ-III Applied Problems subtest, the Child Math Assessment–Abbreviated (CMA-A), and the Shape Composition task. For a more detailed description of these outcome measures, see Appendices A2.1–A2.4.
Staff/teacher training Teachers received curriculum training prior to the start of the 2003–04 school year. This was the second year of implementation of the treatment, and most of the teachers had been trained prior to the start of the 2002–03 school year. New teachers each received 12 hours of training, and returning teachers each received 6 hours of training.

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Appendix A1.2 Study characteristics: Fischel, Bracken, Fuchs-Eisenberg, Spira, Katz, & Shaller, 2007 (randomized controlled trial)

Characteristic Description
Study citation

Fischel, J. E., Bracken, S. S., Fuchs-Eisenberg, A., Spira, E. G., Katz, S., & Shaller, G. (2007). Evaluation of curricular approaches to enhance preschool early literacy skills. Journal of Literacy Research, 39(4), 471–501.
Participants Twenty-seven unique Head Start preschool classrooms in six centers were randomly assigned to one of two curricular approaches overlaid onto their standard curriculum (High/Scope® Educational Approach) and a business-as-usual control group that used only the High/Scope® Educational Approach over three years of the study.1 The two curricula were Let’s Begin with the Letter People® and the Waterford Early Reading™ Level One. In year one of the study, three classrooms were assigned to Let’s Begin with the Letter People® and three to the control group. In year two, the three control group classrooms from year one were randomly assigned to one of the intervention groups, and an additional eight new classrooms joined the study and were randomly assigned to groups; thus, three new classrooms were assigned to Let’s Begin with the Letter People® and five new classrooms participated as the control group. In addition, two randomly selected Let’s Begin with the Letter People® classrooms from year one participated again in year two. In year three, the five control classrooms from the previous year were randomly assigned to one of the intervention groups and three new classrooms participated as the control group. Thus, two new classrooms were assigned to Let’s Begin with the Letter People® and three to the control group, and two randomly selected Let’s Begin with the Letter People® classrooms from previous years also participated in the study.2 Classrooms were divided as follows: Let’s Begin with the Letter People® (12), Waterford Early Reading™ Level One (12), and comparison (11). A total of 507 children attending full-day classes for five days a week participated in the study. Children in the study sample had a mean age of 4 years, 4 months at the time of pretest. The sample of children included African-American (42%), Hispanic (41%), multiracial (8%), Caucasian (7%), and other race/ethnicity (2%). Approximately 14% of the total sample were Spanish-language dominant at Head Start entry.
Setting The study was conducted in 27 unique Head Start classrooms in six centers in southeastern New York State (four centers in year one; one additional center in year two; and one additional center in year three). All centers were part of the same Head Start grantee.
Intervention The intervention group classrooms used the Let’s Begin with the Letter People® curriculum overlaid on the existing High/Scope® curriculum, which all programs had used for at least 10 years before the study. Let’s Begin with the Letter People® is a comprehensive prekindergarten curriculum that is organized thematically. Literacy learning is integrated across topic areas, including science, health and safety, art, math, spatial concepts, and music, as well as development of large and small motor skills. The curriculum focuses on literacy and language skills, including oral language, phonological and phonemic awareness, and letter knowledge. The curriculum lessons address the development of letter knowledge in various contexts (for example, circle time, small group, large group) and activities (for example, center activities, story times). Classroom practices include teacher-directed activities, application of skills, and independent practice with activities that are tied to the curriculum. Let’s Begin with the Letter People® classroom is based on centers (for example, Paint Corner, Block, Drama Center, Mathematics). Curriculum materials include Letter People Huggables®. Each Letter Person represents a letter of the alphabet and has distinguishing characteristics that are readily associated with the sound represented by the letter.
Comparison The business-as-usual comparison group classrooms used the standard classroom curriculum (High/Scope®), which prescribes a daily routine (planning time, work time, cleanup time, time for recall, large-group time, small-group time, and outdoor play) and aligns well with Head Start’s performance standards, focusing on language, literacy, and other school readiness skills, such as numeracy, reasoning, problem solving, and decisionmaking.
Primary outcomes and measurement The outcome domains assessed were children’s oral language and print knowledge. Oral language was assessed with the Peabody Picture Vocabulary Test–III (PPVT-III; a standardized measure) and the Story Comprehension subtest (a nonstandardized measure). Print knowledge was assessed using six measures: the Woodcock-Johnson–Revised (WJ-R) Letter-Word Identification subtest, the WJ-R Dictation subtest (both standardized measures), the Get Ready to Read! (GRTR) screening instrument (a nonstandardized measure), and the Letter Knowledge, Book Knowledge, and Print Conventions subtests of the storybook assessment developed for the Head Start FACES study (nonstandardized measures). For a more detailed description of these outcome measures, see Appendices A2.1–A2.4.
Staff/teacher training Teachers and teacher assistants in the Let’s Begin with the Letter People® group participated in a three-day curriculum training each August conducted by a professional trainer from Abrams and Company (the developer and distributor of this curriculum). The trainer visited each classroom in the Let’s Begin with the Letter People® condition in the fall and spring of each intervention year and provided individual feedback to teachers. Fidelity was measured during these visits using a checklist to assess the degree of implementation in two domains: Classroom Organization and Teacher Behavior. Implementation by all teachers in each year of the study was determined to be accurate and appropriate. Fischel et al. (2007) reported that additional training was offered by the trainer; however, details of the frequency, content, or degree of participation in these trainings were not provided. Teachers and assistants in the Let’s Begin with the Letter People® group and the business-as-usual comparison group participated in a week-long in-service High/Scope® curriculum training at the beginning of the school year. Support was provided in the classroom by educational and child development specialists throughout the school year.
1 For the rating of effectiveness in this WWC intervention report, the WWC includes only the results comparing the Let’s Begin with the Letter People® group to the business-as-usual comparison group; however, results for the comparison between the curricula are included in Appendices A4.5 and A4.6. The WWC includes the Waterford Early Reading™ Level One versus business-as-usual comparison in a separate Waterford Early Reading™ Level One intervention report. Both intervention groups used the studied intervention in conjunction with the High/Scope® curriculum, which was the standard curriculum used by the classrooms prior to the study.
2 The same process yielded three Waterford Early Reading™ Level One classrooms in year one, five Waterford Early Reading™ Level One classrooms (three new classrooms and two repeat classrooms) in year two, and four Waterford Early Reading™ Level One classrooms (two new classrooms and two repeat classrooms) in year three. The WWC includes the data only from children in classrooms new to their study group in each year because families of children attending in the second year of the intervention may have selected the classroom because of its curriculum.

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Appendix A2.1 Outcome measures for the oral language domain

Outcome measure Description
Peabody Picture Vocabulary Test–III (PPVT-III) A standardized measure of children’s receptive vocabulary in which children show understanding of a spoken word by pointing to a picture that best represents the meaning (as cited in Fischel et al., 2007, and PCER Consortium, 2008).
Test of Language Development–Primary: III (TOLD-P:3) Grammatic Understanding subtest A standardized measure of children’s ability to comprehend the meaning of sentences by selecting pictures that most accurately represent the sentence (as cited in PCER Consortium, 2008).
Comprehension An adaptation of prereading assessments developed by Clay (1979), Teale (1988, 1990), and Mason and Stewart (1989) for use in the Family and Child Experiences Study (FACES). The child is handed a storybook and asked a series of questions about the characters and plot (as cited in Fischel et al., 2007).

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Appendix A2.2 Outcome measures for the print knowledge domain

Outcome measure Description
Test of Early Reading Ability–III (TERA-3) A standardized measure of children’s developing reading skills with three subtests: Alphabet, Conventions, and Meaning (as cited in PCER Consortium, 2008).1
Woodcock Johnson–III (WJ-III) Letter-Word Identification subtest A standardized measure of identification of letters and reading of words (as cited in PCER Consortium, 2008).
Woodcock-Johnson–Revised (WJ-R) Letter-Word Identification subtest A standardized measure of identification of letters and reading of words (as cited in Fischel et al., 2007).
Woodcock-Johnson–III (WJ-III) Spelling subtest A standardized measure that assesses children’s prewriting skills, such as drawing lines, tracing, and writing letters (as cited in PCER Consortium, 2008).
Woodcock-Johnson–Revised (WJ-R) Dictation subtest A standardized measure that assesses children’s prewriting skills, such as drawing lines, tracing, and writing letters (as cited in Fischel et al., 2007).
Get Ready to Read! (GRTR) Screen A 20-question, nonstandardized screening test designed to measure emergent writing skills (identifying best picture exemplars), linguistic awareness (rhyming, segmenting words, and deletion of sounds), and print knowledge (differentiating print from pictures, letter naming, and identifying letter sounds) (as cited in Fischel et al., 2007).
Letters Known A test developed for FACES requiring the child to identify as many letters as possible from uppercase arrays of letters (as cited in Fischel et al., 2007).
Book Knowledge A test developed for FACES in which a child is handed a book that is inverted and backwards and asked a series of questions about book knowledge (for example, where is the front of the book, demonstrate how to open a book, and locate the title and the author’s name) (as cited in Fischel et al., 2007).
Print Conventions A test developed for FACES using a storybook, in which a child is asked to identify print conventions (for example, reading from left to right and top to bottom, location of page start, page turning) (as cited in Fischel et al., 2007).
1 By name, this measure sounds as if it should be captured under the Early Reading and Writing domain; however, the description of the measure identifies constructs that are pertinent to Print Knowledge, such as knowing the alphabet, understanding print conventions, and environmental print.

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Appendix A2.3 Outcome measures for the phonological processing domain

Outcome measure Description
Preschool Comprehensive Test of Phonological and Print Processing (Pre-CTOPPP), Elision subtest A measure of children’s ability to identify and manipulate sounds in spoken words, using word prompts and picture plates for the first nine items and word prompts only for later items (as cited in PCER Consortium, 2008).

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Appendix A2.4 Outcome measures for the math domain

Outcome measure Description
Woodcock-Johnson–III (WJ-III) Applied Problems subtest A standardized measure of children’s ability to solve numerical and spatial problems, presented verbally with accompanying pictures of objects (as cited in PCER Consortium, 2008).
Child Math Assessment–Abbreviated (CMA-A) Composite Score The average of four subscales: (1) solving addition and subtraction problems using visible objects, (2) constructing a set of objects equal in number to a given set, (3) recognizing shapes, and (4) copying a pattern using objects that vary in color and identity from the model pattern (as cited in PCER Consortium, 2008).
Building Blocks, Shape Composition task Modified for PCER from the Building Blocks assessment tools. Children use blocks to fill in a puzzle and are assessed on whether they fill the puzzle without gaps or hangovers (as cited in PCER Consortium, 2008).

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Appendix A3.1 Summary of study findings included in the rating for the oral language domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size (classrooms/students) Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
PPVT-III Preschoolers 30/184 90.72
(19.18)		 91.33
(18.12)		 –0.61 –0.03 ns –1
TOLD-P:3 Grammatic Understanding Preschoolers 30/184 9.74
(2.73)		 9.33
(2.71)		 0.41 0.08 ns +3
Average for oral language (PCER Consortium, 2008)9 0.03 ns +1
Fischel et al., 2007 (randomized controlled trial)8, 10
PPVT-III Preschoolers 19/272 86.59
(13.80)		 85.72
(13.68)		 0.87 0.06 ns +3
Comprehension Preschoolers 19/277 0.89
(0.77)		 0.90
(0.74)		 –0.01 –0.01 ns –1
Average for oral language (Fischel et al., 2007)9 0.02 ns +1
Domain average for oral language across all studies9 0.03 na +1

ns = not statistically significant
na = not applicable
PPVT-III = Peabody Picture Vocabulary Test–III
TOLD-P:3 = Test of Language Development–Primary-III

1 This appendix reports findings considered for the effectiveness rating and the average improvement indices for the oral language domain. Kindergarten follow-up findings from PCER Consortium (2008) are not included in these ratings but are reported in Appendix A4.1.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the authors (Cohen’s d based on a repeated measures analysis).
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools and for multiple comparisons. For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant. In the case of Fischel et al. (2007), a correction for clustering was needed, so the significance levels may differ from those reported in the original study.
9 The WWC-computed average effect sizes for each study and for the domain across studies are simple averages rounded to two decimal places. The average improvement indices are calculated from the average effect sizes.
10 The WWC analysis of Fischel et al. (2007) focused on teachers new to their study group, whereas the original study reported findings based on analysis of new and experienced teachers; this also may cause the significance levels reported to differ from those reported in the original study. The child-level posttest sample sizes, and posttest means and standard deviations, were provided by the study authors upon WWC request.

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Appendix A3.2 Summary of study findings included in the rating for the print knowledge domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size (classrooms/students) Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
TERA-3 Preschoolers 30/183 92.94
(16.06)		 92.76
(17.86)		 0.18 0.02 ns +1
WJ-III Letter-Word Preschoolers 30/184 108.72
(12.54)		 106.04
(13.82)		 2.68 0.10 ns +4
WJ-III Spelling Preschoolers 30/184 101.34
(13.01)		 97.37
(12.63)		 3.97 0.17 ns +7
Average for print knowledge (PCER Consortium, 2008)9 0.10 ns +4
Fischel et al., 2007 (randomized controlled trial)8, 10
WJ-R Letter-Word Identification Preschoolers 19/235 98.08
(12.06)		 96.69
(11.90)		 1.39 0.12 ns +5
WJ-R Dictation Preschoolers 19/194 93.48
(15.48)		 88.93
(15.03)		 4.55 0.30 ns +12
Get Ready to Read! Screen Preschoolers 19/281 12.62
(3.70)		 11.59
(3.83)		 1.03 0.27 ns +11
Letters Known Preschoolers 19/277 17.80
(9.01)		 15.86
(9.68)		 1.94 0.21 ns +8
Book Knowledge Preschoolers 19/277 2.85
(1.37)		 2.53
(1.27)		 0.32 0.24 ns +10
Print Conventions Preschoolers 19/277 0.43
(0.74)		 0.27
(0.60)		 0.16 0.24 ns +9
Average for print knowledge (Fischel et al., 2007)9 0.23 ns +9
Domain average for print knowledge across all studies9 0.16 na +6

ns = not statistically significant
na = not applicable
TERA-3 = Test of Early Reading Ability–III
WJ-III = Woodcock-Johnson–III
WJ-R = Woodcock-Johnson–Revised

1 This appendix reports findings considered for the effectiveness rating and the average improvement indices for the print knowledge domain. Kindergarten follow-up findings from PCER Consortium (2008) are not included in these ratings but are reported in Appendix A4.2.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the authors (Cohen’s d based on a repeated measures analysis).
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools and for multiple comparisons. For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant. In the case of Fischel et al. (2007), a correction for clustering was needed, so the significance levels may differ from those reported in the original study.
9 The WWC-computed average effect sizes for each study and for the domain across studies are simple averages rounded to two decimal places. The average improvement indices are calculated from the average effect sizes.
10 The WWC analysis of Fischel et al. (2007) focused on teachers new to their study group, whereas the original study reported findings based on analysis of new and experienced teachers; this also may cause the significance levels reported to differ from those reported in the original study. The child-level posttest sample sizes, and posttest means and standard deviations, were provided by the study authors upon WWC request.

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Appendix A3.3 Summary of study findings included in the rating for the phonological processing domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size (classrooms/students) Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
Pre-CTOPPP Elision subtest Preschoolers 30/184 9.35
(5.07)		 10.11
(4.64)		 –0.76 –0.13 ns –5
Domain average for phonological processing9 –0.13 ns –5

ns = not statistically significant
Pre-CTOPPP = Preschool Comprehensive Test of Phonological and Print Processing

1 This appendix reports findings considered for the effectiveness rating and the average improvement indices for the phonological processing domain. Kindergarten follow-up findings from PCER Consortium (2008) are not included in these ratings but are reported in Appendix A4.3.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the authors (Cohen’s d based on a repeated measures analysis).
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools and for multiple comparisons. For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.
9 This row provides the study average, which, in this instance, is also the domain average. The WWC-computed domain average effect size is a simple average rounded to two decimal places. The domain improvement index is calculated from the average effect size.

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Appendix A3.4 Summary of study findings included in the rating for the math domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size (classrooms/students) Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
WJ-III Applied Problems subtest Preschoolers 30/184 96.75
(13.25)		 99.28
(16.60)		 –2.53 –0.10 ns –4
CMA-A Composite Preschoolers 30/184 0.69
(0.22)		 0.65
(0.24)		 0.04 0.15 ns +6
Shape Composition Preschoolers 30/184 1.92
(0.95)		 1.72
(0.69)		 0.20 0.21 ns +8
Domain average for math9 0.09 ns +3

ns = not statistically significant
WJ-III = Woodcock-Johnson–III
CMA-A = Child Math Assessment–Abbreviated

1 This appendix reports findings considered for the effectiveness rating and the average improvement indices for the math domain. Kindergarten follow-up findings from PCER Consortium (2008) are not included in these ratings but are reported in Appendix A4.4.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the authors (Cohen’s d based on a repeated measures analysis).
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools and for multiple comparisons. For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.
9 This row provides the study average, which, in this instance, is also the domain average. The WWC-computed domain average effect size is a simple average rounded to two decimal places. The domain improvement index is calculated from the average effect size.

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Appendix A4.1 Summary of follow-up findings for the oral language domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size
(classrooms/students)		 Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
PPVT-III Kindergarten nr/150 93.95
(18.03)		 94.00
(16.01)		 –0.05 0.00 ns 0
TOLD-P:3 Grammatic
Understanding subtest		 Kindergarten nr/151 9.47
(3.12)		 10.08
(2.80)		 –0.61 –0.12 ns –5
ns = not statistically significant
nr = not reported
PPVT-III = Peabody Picture Vocabulary Test–III
TOLD-P:3 = Test of Language Development Primary–III

1 This appendix presents follow-up findings considered for measures that fall in the oral language domain. End-of-preschool scores were used for rating purposes and are presented in Appendix A3.1.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the study authors.
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.

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Appendix A4.2 Summary of follow-up findings for the print knowledge domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size
(classrooms/students)		 Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
TERA-3 Kindergarten nr/151 92.65
(18.50)		 93.96
(16.47)		 –1.31 –0.13 ns –5
WJ-III Letter-Word
Identification		 Kindergarten nr/151 104.75
(13.44)		 109.53
(13.57)		 –4.78 –0.18 ns –7
WJ-III Spelling Kindergarten nr/151 101.91
(15.68)		 103.46
(13.14)		 –1.55 –0.06 ns –2

ns = not statistically significant
nr = not reported
TERA-3 = Test of Early Reading Ability–III
WJ-III = Woodcock-Johnson–III

1 This appendix presents follow-up findings considered for measures that fall in the print knowledge domain. End-of-preschool scores were used for rating purposes and are presented in Appendix A3.2.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the study authors.
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.

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Appendix A4.3 Summary of follow-up findings for the phonological processing domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size
(classrooms/students)		 Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
CTOPP Elision subtest Kindergarten nr/151 4.52
(3.66)		 5.04
(4.24)		 –0.52 –0.13 ns –5

ns = not statistically significant
nr = not reported
CTOPP = Comprehensive Test of Phonological Processing

1 This appendix presents follow-up findings considered for measures that fall in the phonological processing domain. End-of-preschool scores were used for rating purposes and are presented in Appendix A3.3.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the study authors.
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.

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Appendix A4.4 Summary of follow-up findings for the math domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size
(classrooms/students)		 Let’s Begin with the Letter People® group3 Comparison group Mean difference4 (Let’s Begin with the Letter People®– comparison) Effect size5 Statistical significance6
(at α = 0.05)		 Improvement index7
PCER Consortium, 2008 (randomized controlled trial)8
WJ-III Applied Problems Kindergarten nr/151 99.18
(13.42)		 102.40
(11.38)		 –3.22 –0.13 ns –5
CMA-A Composite Kindergarten nr/151 0.70
(0.18)		 0.72
(0.14)		 –0.02 –0.07 ns –3
Shape Composition Kindergarten nr/151 2.45
(0.77)		 2.51
(0.69)		 –0.06 –0.06 ns –2
ns = not statistically significant
nr = not reported
WJ-III = Woodcock-Johnson–III
CMA-A = Child Math Assessment–Abbreviated

1 This appendix presents follow-up findings considered for measures that fall in the math domain. End-of-preschool scores were used for rating purposes and are presented in Appendix A3.4.
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 In PCER Consortium (2008), the treatment group mean equals the sum of the unadjusted control group mean and the covariate-adjusted mean difference. Standard deviations are unadjusted.
4 Positive differences and effect sizes favor the intervention group; negative differences and effect sizes favor the comparison group. In the case of PCER Consortium (2008), the mean differences are covariate adjusted.
5 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B. In the case of PCER Consortium (2008), the WWC used the effect sizes reported by the study authors.
6 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
7 The improvement index represents the difference between the percentile rank of the average student in the intervention condition and that of the average student in the comparison condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.
8 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of PCER Consortium (2008), no corrections were needed because the analysis corrected for clustering by using HLM and no impacts were statistically significant.

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Appendix A4.5 Summary of findings for comparisons between Let’s Begin with the Letter People® and Waterford Early Reading™ Level One for the oral language domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size3
(classrooms/students)		 Let’s Begin with the Letter People® group4 Waterford Early Reading™ Level One group4 Mean difference5
(Let’s Begin with the Letter People®– Waterford Early Reading™ Level One)		 Effect size6 Statistical significance7
(at α = 0.05)		 Improvement index8
Fischel et al., 2007 (randomized controlled trial)9
PPVT-III Preschoolers 16/241 86.59
(13.80)		 86.92
(14.39)		 –0.33 –0.02 ns –1
Comprehension Preschoolers 16/247 0.89
(0.77)		 0.85
(0.76)		 0.04 0.05 ns +2

ns = not statistically significant
PPVT-III = Peabody Picture Vocabulary Test–III

1 This appendix reports findings for the head-to-head comparison of Let’s Begin with the Letter People® and Waterford Early Reading™ Level One. Comparisons of Let’s Begin with the Letter People® and the business-as-usual comparison group were used for rating purposes and are presented in Appendix A3.1. The WWC includes data from children participating in classrooms that had not participated in previous waves (that is, children from unique classrooms).
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 The child-level posttest sample sizes were provided by the study authors upon WWC request.
4 The posttest means are covariate-adjusted means provided by the study authors upon WWC request.
5 Positive differences and effect sizes favor the Let’s Begin with the Letter People® group; negative differences and effect sizes favor the Waterford Early Reading™ Level One group.
6 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B.
7 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
8 The improvement index represents the difference between the percentile rank of the average student in the Let’s Begin with the Letter People® condition and that of the average student in the Waterford Early Reading™ Level One condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the Let’s Begin with the Letter People® group.
9 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of Fischel et al. (2007), a correction for clustering was needed, so the significance levels may differ from those reported in the original study.

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Appendix A4.6 Summary of findings for comparisons between Let’s Begin with the Letter People® and Waterford Early Reading™ Level One for the print knowledge domain1

  Authors' findings
from the study		  
  Mean outcome
(standard deviation)2		 WWC calculations
Outcome measure Study sample Sample size3
(classrooms/students)		 Let’s Begin with the Letter People® group4 Waterford Early Reading™ Level One group4 Mean difference5
(Let’s Begin with the Letter People®– Waterford Early Reading™ Level One)		 Effect size6 Statistical significance7
(at α = 0.05)		 Improvement index8
Fischel et al., 2007 (randomized controlled trial)9
WJ-R Letter-Word
Identification subtest		 Preschoolers 16/208 98.08
(12.06)		 98.69
(11.41)		 –0.61 –0.05 ns –2
WJ-R Dictation Preschoolers 16/173 93.48
(15.48)		 90.37
(14.28)		 3.11 0.21 ns +8
Get Ready to Read!
Screen		 Preschoolers 16/251 12.62
(3.70)		 12.84
(3.87)		 –0.22 –0.06 ns –2
Letters Known Preschoolers 16/247 17.80
(9.01)		 18.03
(8.81)		 –0.23 –0.03 ns –1
Book Knowledge Preschoolers 16/247 2.85
(1.37)		 2.41
(1.37)		 0.44 0.32 ns +13
Print Conventions Preschoolers 16/247 0.43
(0.74)		 0.44
(0.77)		 –0.01 –0.01 ns –1

ns = not statistically significant
WJ-R = Woodcock-Johnson–Revised

1 This appendix reports findings for the head-to-head comparison of Let’s Begin with the Letter People® and Waterford Early Reading™ Level One. Comparisons of Let’s Begin with the Letter People® and the business-as-usual comparison group were used for rating purposes and are presented in Appendix A3.2. The WWC includes data from children participating in classrooms that had not participated in previous waves (that is, children from unique classrooms).
2 The standard deviation across all students in each group shows how dispersed the participants’ outcomes are: a smaller standard deviation on a given measure would indicate that participants had more similar outcomes.
3 The child-level posttest sample sizes were provided by the study authors upon WWC request.
4 The posttest means are covariate-adjusted means provided by the study authors upon WWC request.
5 Positive differences and effect sizes favor the Let’s Begin with the Letter People® group; negative differences and effect sizes favor the Waterford Early Reading™ Level One group.
6 For an explanation of the effect size calculation, see WWC Procedures and Standards Handbook, Appendix B.
7 Statistical significance is the probability that the difference between groups is a result of chance rather than a real difference between the groups.
8 The improvement index represents the difference between the percentile rank of the average student in the Let’s Begin with the Letter People® condition and that of the average student in the Waterford Early Reading™ Level One condition. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the Let’s Begin with the Letter People® group.
9 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools (corrections for multiple comparisons were not done for findings not included in the overall intervention rating). For an explanation about the clustering correction, see the WWC Tutorial on Mismatch. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. For Fischel et al. (2007), a correction for clustering was needed, so the significance levels may differ from those reported in the original study.

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Appendix A5.1 Let’s Begin with the Letter People® rating for the oral language domain

The WWC rates an intervention’s effects for a given outcome domain as positive, potentially positive, mixed, no discernible effects, potentially negative, or negative.1

For the outcome domain of oral knowledge, the WWC rated Let’s Begin with the Letter People® as having no discernible effects.

Rating received

No discernible effects: No affirmative evidence of effects.

  • Criterion 1: None of the studies shows a statistically significant or substantively important effect, either positive or negative.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important effect, either positive or negative.
Other ratings considered

Positive effects: Strong evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant positive effects, at least one of which met WWC evidence standards for a strong design.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant positive effect.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important negative effects.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important negative effect.

Potentially positive effects: Evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important positive effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important negative effect and fewer or the same number of studies showing indeterminate effects than showing statistically significant or substantively important positive effects.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important negative effect. Neither study showed a statistically significant or substantively important positive effect on oral language.

Mixed effects: Evidence of inconsistent effects as demonstrated through either of the following criteria.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect, and at least one study showing a statistically significant or substantively important negative effect, but no more such studies than the number showing a statistically significant or substantively important positive effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important positive or negative effect.

    OR

  • Criterion 2: At least one study showing a statistically significant or substantively important effect, and more studies showing an indeterminate effect than showing a statistically significant or substantively important effect.

    Not met. Neither study of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important positive or negative effect.

Potentially negative effects: Evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important negative effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important negative effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important positive effect, or more studies showing statistically significant or substantively important negative effects than showing statistically significant or substantively important positive effects.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important positive effect. Neither study showed a statistically significant or substantively important negative effect on oral language.

Negative effects: Strong evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant negative effects, at least one of which met WWC evidence standards for a strong design.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant negative effect.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important positive effects.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured oral language showed a statistically significant or substantively important positive effect.

1 For rating purposes, the WWC considers the statistical significance of individual outcomes and the domain-level effect. The WWC also considers the size of the domain-level effect for ratings of potentially positive or potentially negative effects. For a complete description, see the WWC Procedures and Standards Handbook, Appendix E.

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Appendix A5.2 Let’s Begin with the Letter People® rating for the print knowledge domain

The WWC rates an intervention’s effects for a given outcome domain as positive, potentially positive, mixed, no discernible effects, potentially negative, or negative.1

For the outcome domain of print knowledge, the WWC rated Let’s Begin with the Letter People® as having no discernible effects.

Rating received

No discernible effects: No affirmative evidence of effects.

  • Criterion 1: None of the studies shows a statistically significant or substantively important effect, either positive or negative.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important effect, either positive or negative.
Other ratings considered

Positive effects: Strong evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant positive effects, at least one of which met WWC evidence standards for a strong design.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant positive effect.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important negative effects.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important negative effect.

Potentially positive effects: Evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important positive effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important negative effect and fewer or the same number of studies showing indeterminate effects than showing statistically significant or substantively important positive effects.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important negative effect. Neither study showed a statistically significant or substantively important positive effect on print knowledge.

Mixed effects: Evidence of inconsistent effects as demonstrated through either of the following criteria.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect, and at least one study showing a statistically significant or substantively important negative effect, but no more such studies than the number showing a statistically significant or substantively important positive effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important positive or negative effect.

    OR

  • Criterion 2: At least one study showing a statistically significant or substantively important effect, and more studies showing an indeterminate effect than showing a statistically significant or substantively important effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important positive or negative effect.

Potentially negative effects: Evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important negative effect.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important negative effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important positive effect, or more studies showing statistically significant or substantively important negative effects than showing statistically significant or substantively important positive effects.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important positive effect. Neither study showed a statistically significant or substantively important negative effect on print knowledge.

Negative effects: Strong evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant negative effects, at least one of which met WWC evidence standards for a strong design.

    Not met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant negative effect.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important positive effects.

    Met. Neither of the two studies of Let’s Begin with the Letter People® that measured print knowledge showed a statistically significant or substantively important positive effect.

1 For rating purposes, the WWC considers the statistical significance of individual outcomes and the domain-level effect. The WWC also considers the size of the domain-level effect for ratings of potentially positive or potentially negative effects. For a complete description, see the WWC Procedures and Standards Handbook, Appendix E.

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Appendix A5.3 Let’s Begin with the Letter People® rating for the phonological processing domain

The WWC rates an intervention’s effects for a given outcome domain as positive, potentially positive, mixed, no discernible effects, potentially negative, or negative.1

For the outcome domain of phonological processing, the WWC rated Let’s Begin with the Letter People® as having no discernible effects.

Rating received

No discernible effects: No affirmative evidence of effects.

  • Criterion 1: None of the studies shows a statistically significant or substantively important effect, either positive or negative.

    Met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important effect, either positive or negative.
Other ratings considered

Positive effects: Strong evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant positive effects, at least one of which met WWC evidence standards for a strong design.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant positive effect.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important negative effects.

    Met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important negative effect.

Potentially positive effects: Evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important positive effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important negative effect and fewer or the same number of studies showing indeterminate effects than showing statistically significant or substantively important positive effects.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important negative effect. No other studies measured phonological processing.

Mixed effects: Evidence of inconsistent effects as demonstrated through either of the following criteria.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect, and at least one study showing a statistically significant or substantively important negative effect, but no more such studies than the number showing a statistically significant or substantively important positive effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important positive or negative effect. No other studies measured phonological processing.

    OR

  • Criterion 2: At least one study showing a statistically significant or substantively important effect, and more studies showing an indeterminate effect than showing a statistically significant or substantively important effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important positive or negative effect. No other studies measured phonological processing.

Potentially negative effects: Evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important negative effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important negative effect. No other studies measured phonological processing.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important positive effect, or more studies showing statistically significant or substantively important negative effects than showing statistically significant or substantively important positive effects.

    Met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important positive effect. No other studies measured phonological processing.

Negative effects: Strong evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant negative effects, at least one of which met WWC evidence standards for a strong design.

    Not met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant negative effect. No other studies measured phonological processing.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important positive effects.

    Met. The one study of Let’s Begin with the Letter People® that measured phonological processing showed no statistically significant or substantively important positive effect. No other studies measured phonological processing.

1 For rating purposes, the WWC considers the statistical significance of individual outcomes and the domain-level effect. The WWC also considers the size of the domain-level effect for ratings of potentially positive or potentially negative effects. For a complete description, see the WWC Procedures and Standards Handbook, Appendix E.

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Appendix A5.4 Let’s Begin with the Letter People® rating for the math domain

The WWC rates an intervention’s effects for a given outcome domain as positive, potentially positive, mixed, no discernible effects, potentially negative, or negative.1

For the outcome domain of math, the WWC rated Let’s Begin with the Letter People® as having no discernible effects.

Rating received

No discernible effects: No affirmative evidence of effects.

  • Criterion 1: None of the studies shows a statistically significant or substantively important effect, either positive or negative.

    Met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important effect, either positive or negative.
Other ratings considered

Positive effects: Strong evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant positive effects, at least one of which met WWC evidence standards for a strong design.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant positive effect on math.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important negative effects.

    Met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important negative effect.

Potentially positive effects: Evidence of a positive effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important positive effect.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important negative effect and fewer or the same number of studies showing indeterminate effects than showing statistically significant or substantively important positive effects.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important negative effect.

Mixed effects: Evidence of inconsistent effects as demonstrated through either of the following criteria.

  • Criterion 1: At least one study showing a statistically significant or substantively important positive effect, and at least one study showing a statistically significant or substantively important negative effect, but no more such studies than the number showing a statistically significant or substantively important positive effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important positive or negative effect. No other studies measured math.

    OR

  • Criterion 2: At least one study showing a statistically significant or substantively important effect, and more studies showing an indeterminate effect than showing a statistically significant or substantively important effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important positive or negative effect. No other studies measured math.

Potentially negative effects: Evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: At least one study showing a statistically significant or substantively important negative effect.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important negative effect. No other studies measured math.

    AND

  • Criterion 2: No studies showing a statistically significant or substantively important positive effect, or more studies showing statistically significant or substantively important negative effects than showing statistically significant or substantively important positive effects.

    Met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important positive effect. No other studies measured math.

Negative effects: Strong evidence of a negative effect with no overriding contrary evidence.

  • Criterion 1: Two or more studies showing statistically significant negative effects, at least one of which met WWC evidence standards for a strong design.

    Not met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant negative effect. No other studies measured math.

    AND

  • Criterion 2: No studies showing statistically significant or substantively important positive effects.

    Met. The one study of Let’s Begin with the Letter People® that measured math showed no statistically significant or substantively important positive effect. No other studies measured math.

1 For rating purposes, the WWC considers the statistical significance of individual outcomes and the domain-level effect. The WWC also considers the size of the domain-level effect for ratings of potentially positive or potentially negative effects. For a complete description, see the WWC Procedures and Standards Handbook, Appendix E.

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Appendix A6 Extent of evidence by domain

  Sample size
Outcome domain Number of studies Preschool classrooms Students2 Extent of evidence1
Oral language 2 49 456 Medium to large
Print knowledge 2 49 377 Medium to large
Phonological processing 1 30 184 Small
Early reading or writing 0 na na na
Cognition 0 na na na
Math 1 30 184 Small

na = not applicable/not studied

1 A rating of “medium to large” requires at least two studies and two schools across studies in one domain and a total sample size across studies of at least 350 students or 14 classrooms. Otherwise, the rating is “small.”
2 The sample size of students shown in this table is based on the smallest number of children with valid posttest measurements within a domain. Posttest responses for the PCER (2008) study ranged from 183 to 184. Posttest responses for the Fischel et al. (2007) study ranged from 194 to 281, primarily because many Spanish-language-dominant children in the sample could not complete the standardized assessments in English.

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