Found effects

The WWC found the modified version of the Wilson Reading System® used in this study to have potentially positive effects on alphabetics and no discernible effects on fluency and 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 alphabetics is +13 percentile points across all findings in the single study, with a range of +6 to +22 percentile points. The improvement index for the fluency outcome is +6 percentile points in the single study. The average improvement index for comprehension is +7 percentile points across all findings in the study, with a range of +3 to +11 percentile points.

Summary

The WWC reviewed nine studies on Wilson Reading System®. One study met WWC evidence standards, and the remaining studies did not meet WWC evidence screens. Based on this one study, the WWC found potentially positive effects in alphabetics, and no discernible effects in fluency and comprehension. It should be noted, however, that the fluency, comprehension, and vocabulary components of the Wilson Reading System® were not used at the request of the researchers conducting the study. The evidence presented in this report is limited and may change as new research emerges.