Concerning the analysis of 2 x 2 tables.
Recent papers (R. M. Engeman and G. D. Swanson, 1991, Comput. Biomed. Res. 24, 509; M. R. Massai and P. Barbini, 1993, Comput. Biomed Res. 26, 98) have expressed concern regarding differences in results among statistical methods of hypothesis testing for 2 x 2 contingency tables. These papers did not present current statistical thought on this topic, and they did not discuss measures of effect for such analyses. In this paper statistical literature on the 2 x 2 contingency table is presented and philosophical issues underlying the methods discussed. Measures of effect appropriate for several data origins or designs which result in 2 x 2 arrays are also presented. The paper presents an empirical adjustment to the Fisher's exact test known as the mid-P approach. The information should help provide the user of statistics a better understanding of the analysis of 2 x 2 tables. An example using data from Engeman and Swanson (1991) is provided, and some recommendations for the analysis of 2 x 2 tables are given.
O'Brien
K F
KF
School of Allied Health Sciences, East Carolina University, Greenville, North Carolina 27858.
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