Found effects

The WWC found Read Naturally to have no discernible effects on fluency and reading comprehension

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.

The average improvement index for fluency is +8 percentile points across the two studies, with a range of +6 to +9 percentile points across findings. The average improvement index for reading comprehension is +2 percentile points in the one study, with a range of –3 to +9 percentile points across findings.

Summary

The WWC reviewed 14 studies on Read Naturally. One of these studies meets WWC evidence standards; one study meets WWC evidence standards with reservations; the remaining 12 studies do not meet either WWC evidence standards or eligibility screens. Based on these two studies, the WWC found no discernible effects in the fluency or reading comprehension domains. The conclusions presented in this report may change as new research emerges.