Rokhsareh ghorbani moghaddam let me rephrase the information that I got from your post:

Hope it helps!

Best,

Alexander

thanks

my understanding of your post is that post hoc tests can not be run for two groups.right?

besides, how should the treatment variable be entered into spss?

should we assign a value for its description in spss.

many thanks

Rokhsareh ghorbani moghaddam Correct. There is no need for a post-hoc test because there is no additional information that can be retrieved from further tests - there are only two group means to be tested for differences, and the main effect would show whether these two differ significantly from each other. In other words, there is not post-hoc relationship to test for.

What you would run is a repeated measures general linear model (SPSS: Analyze --> General Linear Models --> Repeated Measures). You define your within-subjects variable as the factor1 and define it as having two levels. Than you add the two variables that represent the pre- and post-test measure. Once you click on "define" you can enter the treatment variable as the between subjects factor and covariates if you want to include them.

thanks alot.