Create A/B tests by chatting with AI and launch them on your website within minutes.

Try it for FREE now

Chi-square Test

Quick answer

A chi-square test is a statistical method used to determine whether there is a significant association between categorical variables, most commonly applied in A/B testing to compare conversion rates or other binary outcome metrics between variations.

Key takeaways

  • Chi-square Test helps evaluate whether an experiment result is reliable enough to act on.
  • It should be reviewed together with sample size, duration, effect size, and business impact.
  • It is most useful when the hypothesis and primary metric are defined before the test starts.

Definition

A chi-square test is a statistical method used to determine whether there is a significant association between categorical variables, most commonly applied in A/B testing to compare conversion rates or other binary outcome metrics between variations.

What Chi-square Test means in A/B testing

The chi-square test compares observed frequencies (actual conversions and non-conversions in each variation) against expected frequencies (what would occur if there were no difference between variations). It produces a test statistic and p-value that indicate whether the observed pattern of results is likely due to the test variation or random chance. This test is ideal for analyzing proportions, percentages, and count data.

Why Chi-square Test matters

Chi-square tests are the standard statistical method for evaluating A/B tests focused on conversion rates, click-through rates, and other percentage-based metrics. They provide a rigorous framework for decision-making about whether to implement changes based on binary outcomes. Most A/B testing platforms use chi-square tests or similar methods under the hood to calculate statistical significance for conversion metrics.

Example of Chi-square Test

In testing two different call-to-action buttons, you observe 450 conversions from 10,000 visitors in variation A versus 520 conversions from 10,000 visitors in variation B. A chi-square test determines whether this difference in conversion rates (4.5% vs 5.2%) is statistically significant or could reasonably occur by chance.

How to use Chi-square Test

Use Chi-square Test after you have chosen a primary metric and collected enough traffic for a reliable read. Avoid checking it in isolation; compare it with effect size, confidence, practical impact, and whether the test ran long enough to cover normal traffic patterns.

Common mistake

A common mistake is treating Chi-square Test as a yes-or-no shortcut while ignoring sample size, test duration, and practical business impact. A statistically interesting result can still be too small, too noisy, or too risky to ship.

Related A/B testing terms

FAQ

What does chi-square test mean in A/B testing?

A chi-square test is a statistical method used to determine whether there is a significant association between categorical variables, most commonly applied in A/B testing to compare conversion rates or other binary outcome metrics between variations.

Why does chi-square test matter for experiments?

Chi-square tests are the standard statistical method for evaluating A/B tests focused on conversion rates, click-through rates, and other percentage-based metrics. They provide a rigorous framework for decision-making about whether to implement changes based on binary outcomes. Most A/B testing platforms use chi-square tests or similar methods under the hood to calculate statistical significance for conversion metrics.

How should teams use chi-square test in an experiment?

Use Chi-square Test after you have chosen a primary metric and collected enough traffic for a reliable read. Avoid checking it in isolation; compare it with effect size, confidence, practical impact, and whether the test ran long enough to cover normal traffic patterns.

Download our free 100 point Ecommerce CRO Checklist

This comprehensive checklist covers all critical pages, from homepage to checkout, giving you actionable steps to boost sales and revenue.