Sample size determination/verification

Question

I am going to conduct a survey in order to collect information for two variables and then calculate the correlation between them.

If we assume that $alpha$ = 0.05, $power=0.80$. Can someone show me a step by step method of how a sample of 85 was determined with a medium effect size? And is there a procedure in SAS I can use?

Thanks.

Answer 1

In SAS you can use PROC POWER. Something like

proc power;
   onecorr dist=fisherz
      nullcorr = 0.00
      corr = 0.10 to .9 by .1
      ntotal = .
      power = .8;
run;

seems to do what you want. Definitions of 'medium' can, of course, vary; many people use the definition suggested by Jacob Cohen.