Chi-Squared sample size calculator for clinical trials

Chi-Squared sample size calculator for clinical trials

You can use the Chi-Squared test to analyse your trial data or A/B test data if you have two groups with a dichotomous outcome. For example, you have two arms in your trial: the placebo and the intervention arm, and your endpoint is either yes or no, such as “did the subject experience an adverse event during the trial”.

The calculator below will calculate the minimum sample size for you. Your expected effect size w is the standardised effect size according to Cohen’s definition. You can estimate your expected effect size from the literature. An effect size is considered small if w = 0.10, medium if w = 0.30 and large if w = 0.50.[1]

You may also be interested in our Bayesian A/B test calculator.

Chi-Squared Sample Size Calculator by Fast Data Science
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References

  1. Abdul Rahman, Hanif, et al. Practical guide to calculate sample size for chi-square test in biomedical research. BMC Medical Research Methodology 25.1 (2025): 144.
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Creating a per-subject budget from the charge master

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