I have a matched case-control study with 12 cases and two controls for each case. Evaluating our findings, I want to calculate what our sample size must have been to detect a difference found in another study of a different population.

For the sample size calculation, I intended using the mean values from the other study, but apply the standard deviation from our study.

Mean among cases: 3.14

Mean among controls: 1.58

SD: 1.41

Power 80%, significance level 5%.

How can I go about to find out what sample size we would need in our 1:2 matched study? Can I use any of the calculators found here? Any comments on 2-sided versus 1-sided testing? Normally, I use Stata.

Please do not hesitate to request more info if needed. Thank you in advance.