Help using Base SAS procedures

paired t-test - differences by group

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Contributor
Posts: 39

paired t-test - differences by group

I have pre/post data for one group - outcome is a score. I am interested to see if the scores vary by a covariate like gender. If I use the by command in the ttest procedure, it does not give me a significant p value for differences by gender. how can i go about doing this?

Super User
Posts: 17,888

Re: paired t-test - differences by group

I think you need a PROC ANOVA not a T-Test. 

 

 

Contributor
Posts: 39

Re: paired t-test - differences by group

So would be outcome variable be the difference? And my independent would be gender, but do I need to adjust for baseline (pre) scores as well?

Super User
Posts: 17,888

Re: paired t-test - differences by group

Pre-calculate the differences and test if the difference is different between the groups and not equal to 0. 

ie Mean from Group A = Mean from Group B = Mean from Group  = 0

where mean = post-pre score

 

 

 

Super User
Posts: 17,888

Re: paired t-test - differences by group

Also, BY statements splits an analysis for each group. It's the equivalent of doing some repeatedly for each group but they're considered individually. Analyses do not cross between BY groups. 

 

 

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