Question 386:

Asked on September 17, 2008

Tags: ANOVA , Covariate , ANCOVA

1

Answer:

No answer provided yet.

I would also consider running a repeated measures ANOVA on the data if the same subjects are completing both the pre and post test as this will increase the power of your test and increase the chances of detecting differences.

Sounds like the final score on the intervention program takes into account some nuisance variable like difference in reading ability. As far as converting to z-scores, it sounds like you might be able to use just the percentage scores. You could also see what happens when you convert the data to z-scores. So as not to capitalize on chance (since you're running the test twice essentially) use the lower of the two methods and document your procedure.