To get started, download this A/B testing spreadsheet as a template for gathering and prioritizing experiments, recording the results, and finally evaluating your results using the chi-square test calculator.

Simply input the number of trials and successes for each experiment and it will let you know whether the observed effect (e.g. change in conversion rate) of your treatment (e.g. change in size of CTA button) is not due to chance at (95% confidence); in other words, it will let you know whether you should trust your findings.

This is called rejecting the null hypothesis.