Statistical methods in epidemiology. VII. An overview of the x(2) test for2 x 2 contingency table analysis

Purpose: The odds ratio is an appropriate method of analysis for data in 2x 2 contingency tables. However, other methods of analysis exist. One such me thod is based on the chi (2) test of goodness-of-fit. Key players in the de velopment of statistical theory include Pearson, Fisher and Yates. Method: Data are presented in the form of 2x2 contingency tables and a meth od of analysis based on the chi (2) test is introduced. There are many vari ations of the basic test statistic, one of which is the chi (2) test with Y ates' continuity correction. The usefulness (or not) of Yates' continuity c orrection is discussed. Problems of interpretation when the method is appli ed to kxm tables are highlighted. Results: Some properties of the chi (2) the test are illustrated by taking examples from the author's teaching experiences. Conclusion: Journal editors should be encouraged to give both observed and expected cell frequencies so that better information comes out of the chi ( 2) test statistic.