Biochemia Medica, Vol. 23 No. 2, 2013.
Review article
https://doi.org/10.11613/BM.2013.018
The Chi-square test of independence
Mary L. McHugh
; Department of Nursing, School of Health and Human Services, National University, Aero Court, San Diego, California, USA
Abstract
The Chi-square statistic is a non-parametric (distribution free) tool designed to analyze group diffe-rences when the dependent variable is measured at a nominal level. Like all non-parametric statistics, the Chi-square is robust with respect to the distribution of the data. Specifically, it does not require equality of variances among the study groups or homoscedasticity in the data. It permits evaluation of both dichotomous independent variables, and of multiple group studies. Unlike many other non-parametric and some parametric statistics, the calculations needed to compute the Chi-square provi-de considerable information about how each of the groups performed in the study. This richness of detail allows the researcher to understand the results and thus to derive more detailed information from this statistic than from many others.
The Chi-square is a significance statistic, and should be followed with a strength statistic. The Cra-mer’s V is the most common strength test used to test the data when a significant Chi-square result has been obtained. Advantages of the Chi-square include its robustness with respect to distribution of the data, its ease of computation, the detailed information that can be derived from the test, its use in studies for which parametric assumptions cannot be met, and its flexibility in handling data from both two group and multiple group studies. Limitations include its sample size requirements, difficulty of interpretation when there are large numbers of categories (20 or more) in the independent or depen-dent variables, and tendency of the Cramer’s V to produce relative low correlation measures, even for highly significant results.
Keywords
Chi-square; non-parametric; assumptions; categorical data; statistical analysis
Hrčak ID:
103790
URI
Publication date:
15.6.2013.
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