**540**wrote:

I'm reading Design, Analysis and Interpretation of GWAS of Daniel O. Strom.

On chapter 2 I found:

If we have a sample of N unrelated individuals in a population the distribution of A allele counts for each individual follows a binomial with number of trials = 2N and frequency of A allele = p

p can be found as:

```
p = ( 1/2N ) * SUM (niA)
```

Where niA= number of A alleles in individual i

And the variance:

```
( 1/(2N)^2 ) * SUM Var (niA)
```

But, I do not understand why do we have the 2N **squared** in the second equation.

Thank you.

**10**• written 2.7 years ago by GabrielMontenegro •

**540**