I am new here so I hope my post is appropriate!

I have searched the web and this forum and haven't been able to figure out how exactly I need to perform a power analysis for sample size determination (although I admit I didn't scroll through ALL of the results to my search on this forum)...

I am working on an assignment for an upper year undergraduate psychology course for which I need to write a hypothetical research proposal.

I am trying to determine my sample size and understand that I will need perform perform a power analysis and a sample size analysis (a priori).

I would need to perform a 2 way ANOVA so I found this link explaining how to perform a power analysis for 2 way ANOVA in SAS...

https://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_glmpower_a0000000155.htm

I am wondering what data I use to perform this power analysis. Do I select data from relevant literature on my research topic? What if the standard deviation is not reported? Do I create a set of hypothetical data?

Again I apologize if this post is not appropriate. I am not very strong in stats so this is probably a stupid question!

Thanks in advance for any help you may be able to provide!

-C