Why are SNPs with small effect sizes a problem for GWAS?

Question

[joshf]

Why does increasing a sample size increase the power for detecting SNPs with small effect sizes?

[Devon Ryan]

Why do you think? Is this a homework question?

[joshf]

No, it's not, but I'm learning about the GWAS (in this case its disadvantages) for an internship

Answer 1

[Devon Ryan]

Increasing sample size allows you to more confidently measure variability. That leads to an increased ability to discern smaller differences.

Answer 2

[H.Hasani]

You may think of it backwards, e.g. if you have a bowl with 100 colorful balls, and you are interested in the black ones, which their true proportion in this bowl are 5%. Then your average chance of detecting it in 10 balls will be ~ 0.01, i.e. almost none.