Found effects

The WWC found CWPT to have potentially positive effects on general reading achievement

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 improvement index for general reading achievement is +14 percentile points on the one measure in the single study that met WWC evidence standards.

Summary

The WWC reviewed 12 studies on CWPT. One of these studies met WWC evidence standards; the remaining studies did not meet WWC evidence screens. ¹ Based on this one study, the WWC found potentially positive effects on general reading achievement. The evidence presented in this report may change as new research emerges.