# “Fraction of response interested in” — what does it mean?

I am doing a sample size calculation for a survey and am using the formula found at the bottom of this page: http://www.raosoft.com/samplesize.html

In the formula, r is 'the fraction of responses that you are interested'. What is this exactly? I thought it would be the percentage of the population I want to look at, but this is essentially the sample size I need to examine, which is the outcome answer, so that can't be right.

How do you get a value for r?

Thanks!

• Looks like it's referring to the response distribution value that you can enter at the top - i.e. the percentage of subjects you expect to be affected. – naught101 May 10 '12 at 0:30