Confidence Intervals

I want to create a spreadsheet that measures confidence intervals for my advertising. The idea is that to my test webpage, I would have X number of visitors to version A and Y number of visitors to version B. Version A will results in N sales, version B will have M sales.

What I want to do is create a spreadsheet that can tell me with 95% confidence which page sells better.

Thanks,

Jon

This is a statistics problem, not an excel problem.
If you can get someone from the Math forum to give you the appropriate mathematical algorithm,
I'm sure you can then find someone in the ecxel forum to help you implement it in excel.

Mark.