On the practice of dichotomization of quantitative variables
Issue Date
2002Author
MacCallum, Robert C.
Zhang, Shaobo
Preacher, Kristopher J.
Rucker, Derek D.
Type
Article
Metadata
Show full item recordAbstract
The authors examine the practice of dichotomization of quantitative measures, wherein relationships among variables are examined after 1 or more variables have been converted to dichotomous variables by splitting the sample at some point on the scale(s) of measurement. A common form of dichotomization is the median split, where the independent variable is split at the median to form high and low groups, which are then compared with respect to their means on the dependent variable. The consequences of dichotomization for measurement and statistical analyses are illustrated and discussed. The use of dichotomization in practice is described, and justifications that are offered for such usage are examined. The authors present the case that dichotomization is rarely defensible and often will yield misleading results.
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Citation
Psychological Methods, 7, 19-40.
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