We have run A/B tests in the past using a 50/50 split, and have used the power prop function for calculating the sample size using the power.prop.test in R. My question is how do I calculate what my sample size should be, if we want to use a 95/5 split or a 90/10 split. This was mentioned in "R - power.prop.test, prop.test, and unequal sample sizes in A/B tests" about using a 95/5 split but was not fully answered, so any detail with examples would be appreciated.

*Edited: Understood let me clarify. The component that was not covered was actual formula for calculating this out, or the R code.

From the linked question: "This is why you need to use power.prop.test because the split doesn't matter. What matters is that you meet the minimum sample size for each group."

How would I go about calculating for each group using power prop test?


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    $\begingroup$ What exactly was not covered in the answer you refer to? It seems like you question is a duplicate of the one you refer to, so you should be more precise, otherwise it would get closed as a duplicate. $\endgroup$
    – Tim
    Jul 22, 2015 at 20:38
  • $\begingroup$ possible duplicate of R - power.prop.test, prop.test, and unequal sample sizes in A/B tests $\endgroup$ Jul 22, 2015 at 20:49
  • $\begingroup$ @Gung I agree it is a duplicate--but since the duplicate contains five distinct questions, it seems best to accept that not all five were answered there (nor should they be) and to welcome the present attempt to focus on one of those questions. $\endgroup$
    – whuber
    Jul 22, 2015 at 21:25


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