Here’s a quick and easy A/B split test calculator. Simply enter the number of actions taken and the total number of impressions for your control (Sample A). Then enter the number of actions taken and total number of impressions for the challenger (Sample B). Then click the Calculate Split Test Confidence button.
After clicking the button, the page will refresh showing the conversion rates and confidence percentages for both Sample A and Sample B. Whichever sample has the greatest confidence is currently winning. In general the confidence should exceed 95% before declaring a winner.