So, working in web analytics, it's common to use a chi-square test for A/B tests to test statistical significance. I often use a calculator like this: http://www.usereffect.com/split-test-calculator , so if each variation gets 1000 impressions, and A has 100 conversions and B has 200 conversions, I know that, with a 99.9% confidence interval (assuming randomized samples) that B is the winning variation.
But occasionally, I have values that create percentages over 100%, and seem to throw these calculations off.
So, if I'm testing two donation pages, and I want to use the $ values for conversions, how would I go about that? My goal is to make a statistically informed decision about which page is performing better, in terms of its ability to raise more money.
If I have 1000 impressions of each variation, and one variation raises
$2000 off of 200 contributions, and the othe other raises
$2500 off of 100 contributions, what calculation can I use to know if the difference is meaningful?