Help for covariate analysis with Mixed ANOVA
I need help to explain my data.
I'm conducting a mixed ANOVA with one within subject factor (A) and one between subject factor (B). Results show a main effect of A, and an interaction AxB.
However I would like to test anxiety as a covariate assessed by STAI.
First, what is the best way to compute this ? Should I use ANCOVA or just add STAI in covariate box in my ANOVA ?
Secondly, there are two component in STAI, should I compute my analysis for each component individually, or add both in covariate box ?
Finally, I tried to compute this analysis in my ANOVA directly, I added STAI-Y1 in covariate box. So I don't know how explain results. They showed that with covariate main effect of A disappeared, but there was not a main effect of my covariate. What that is mean ?
I did not find articles, tutorials for this design so if you have these tell me.
Have a nice Sunday.