## Definition:

The z-score is the statistical measure of the difference between two randomly drawn samples. It is expressed as the number of standard deviations an element is from the mean. The larger the z-score the higher the probability that the two means have not been drawn from the same population and the difference between the samples is statistically significant.

### Resources:

Conversion marketing – Glossary of Conversion Marketing.

Over 300 tools reviewed – Digital Marketing Toolbox.

A/B testing software – Which A/B testing tools should you choose?

Types of A/B tests – How to optimise your website’s performance using A/B testing.