This free online A/B test calculator shows if case A or case B is better. Moreover, it shows how sure it is that there is a real difference between the two cases and it’s not just the work of coincidence. Higher the certainty level, the more sureness for you about the fact that one is better than the other. Everyone needs to measure sureness, certainty, confidence of the results.
First of all, find out what kinds of things you want to compare. It can be employee A and employee B, or it can be design A and design B, or product A and product B, and so on. Anything. You also need an event that can be measured, that has a count. For example count of visits, count of emails sent, count of people in the experiment or something like these. Then specify what is your conversion, i.e. a special event or a positive case that is a specified subset of all cases. If you have these all, just fill in the four input fields and you will get the ratios, difference and the certainty of the result. The question, the names of events and cases can also be rewritten, despite they are not input fields, but avoid these A/B test common mistakes.