Steenbergen-Hu and Cooper (2013) also examined the effects of ITS for students in elementary school, middle school and high school (see Exercise 14). The results are shown below.

Elementary school              Mean ES = .41             95% CI: (-.01, -84)
Middle school                      Mean ES = .09             95% CI: (.01, .17)
High school                         Mean ES = -.09            95% CI: (-.17, -.02)

1. Using Cohen’s guidelines, how would you interpret the mean effect size for the three school levels?

2. Based on the 95% CI, what would we conclude regarding the statistical significance of the three mean effect sizes?