Help in sample size calculation!

[Danis84]

Hello,

I’ve made a retrospective research and did a sample size calculation and I cannot find the formula I used and cannot get to this number! I need to present my study next month!

n=720, power=80%, p0=0.15, margin of error=5%

 

[katxt]

Your figures don't seem to be in the normal form.
Perhaps you mean effect size = 0.15 and significance level = 0.05
Or are you talking about proportions?

 

[CamilleJosion]

Hi, the formula will depend on the test your are using. For which test did you do that?

 

[katxt]

Or perhaps you are looking for a confidence interval for a proportion?