Trends colliding: aging comprehensive family physicians and the growing complexity of their patients
Premji K, Glazier RH, Green ME, Khan S, Schultz S, Mathews M, Nastos S, Frymire E, Ryan BL. Can Fam Physician. 2025 Jun 16.
This paper demonstrates an inflation of the type I error rate that occurs when testing the statistical significance of a continuous risk factor after adjusting for a correlated continuous confounding variable that has been divided into a categorical variable.
This study used Monte Carlo simulation methods to assess the inflation of the type I error rate when testing the statistical significance of a risk factor after adjusting for a continuous confounding variable that has been divided into categories.
The study found that the inflation of the type I error rate increases with increasing sample size, as the correlation between the risk factor and the confounding variable increases, and with a decrease in the number of categories into which the confounder is divided.
Even when the confounder is divided in a five-level categorical variable, the inflation of the type I error rate remained high when both the sample size and the correlation between the risk factor and the confounder were high.
Austin PC, Brunner LJ. Stat Med. 2004; 23(7):1159-78.
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