sample size for regression analysis

#1
How would I determine the sample size needed for doing a study using continuous variables (3) and two dichotomous variables? This is for a proposal so I have not collected nay data. Is using prior research as a basis adequate?
 

JohnM

TS Contributor
#2
Yes, you can use prior studies, if your study will be very similar, and the prior studies established that their sample sizes were "large enough" to evaluate the research questions.