# Do I correct for two saparate comparisons (each eith multiple n) - Bonferonni Corrections

I am making two separate comparisons between populations - I am comparing the frequency of multiple alleles between populations - Population 1 Vs Population 2 and Population 1 Vs Population 3.

So my resulting data frame of p values will look like this (I have just populated with x's instead of numbers):

        Pop1_vs_Pop2 Pop1_vs_Pop3
Allele1       x            x
Allele2       x            x
Allele3       x            x


So my question is this: with Bonferroni corrections, so I correct by 3 (ie - divide 0.05 by 3 to determine the significance cut off level, since I am running two independent tests at three alleles each), or do I correct by 0.05/6 (the total number of tests)?

## 1 Answer

It depends on whether you want to control the familywise eror rate (FWER) overall, in which case you use $p=\frac{\alpha}{6}$, or to control them within each comparison of two populations, in which case you use $p=\frac{\alpha}{3}$. I recommend the former for reasons of interpretability.