An Educational Tutorial on Fisher’s Exact Test for Medical Researchers
DOI:
https://doi.org/10.13052/jrss0974-8024.1919Keywords:
Fisher’s exact test, biostatistics, epidemiological research, categorical dataAbstract
Fisher’s exact test is a fundamental statistical tool for analyzing associations in 2×2 contingency tables, especially when dealing with small samples or sparse data common in preliminary medical studies. Despite its widespread use, misconceptions regarding its assumptions, application criteria, and interpretation persist. This tutorial provides a structured, practical guide to Fisher’s exact test. We begin with the theoretical foundation, contrasting it with the chi-square test and explaining its reliance on the hypergeometric distribution. The core of the tutorial features step-by-step manual calculations for educational clarity, followed by practical implementation guides using R, SPSS, and Stata. We address common pitfalls, including misuse in large samples, confusion between one- and two-tailed p-values, and the need for multiple testing corrections. Extensions to larger tables via the Fisher-Freeman-Halton test and Monte Carlo simulation are also discussed. By integrating theory with actionable examples, this tutorial aims to enhance statistical literacy and ensure the accurate application of Fisher’s exact test in clinical and epidemiological research, thereby improving the reliability and reproducibility of findings.
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