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Improvement index
The WWC computes an improvement index for each individual finding. In addition, within each outcome domain, the WWC computes an average improvement index for each study and an average improvement index across studies (see Technical Details of WWC-Conducted Computations). The improvement index represents the difference between the percentile rank of the average student in the intervention condition versus the percentile rank of the average student in the comparison condition. Unlike the rating of effectiveness, the improvement index is based entirely on the size of the effect, regardless of the statistical significance of the effect, the study design, or the analyses. The improvement index can take on values between –50 and +50, with positive numbers denoting results favorable to the intervention group.
Curiosity Corner’s average improvement index for oral language is +2 percentile points across the two studies, with a range of –3 to +14 percentile points. For print knowledge, one study showed an average improvement index of +3 percentile points, with a range of +2 to +4 percentile points across findings. For phonological processing, the average improvement index was +7 percentile points based on one study. For cognition, the average improvement index was –3 percentile points across findings in one study, with a range of –4 to –1 percentile points. The average improvement index for math was +4 percentile points from one study, with a range of 0 to +6 percentile points across findings in one study.
Summary
The WWC reviewed three studies of Curiosity Corner. One meets WWC evidence standards, and one meets WWC evidence standards with reservations. One study did not meet eligibility screens. Based on the two studies, the WWC found no discernible effects of Curiosity Corner on oral language, print knowledge, phonological processing, cognition, or math. The conclusions presented in this report may change as new research emerges.
|Institute of Education Sciences
