Almost 40 years ago, Jacob Cohen showed that dichotomization of continuous variables results in a loss of power.[15] Twenty years later, Peter Austin showed in a Monte Carlo simulation that categorizing a continuous variable in a logistic regression results in inflating the rate of finding false positive associations.[16] The type I (false-positive) error rates increases with sample size, with increasing correlation between the confounding variable and outcome of interest, and the number of… [read post]