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Reducing mean squared error in the analysis of stratified epidemiologic studies.

Kalish (1990, Biometrics 46, 493-499) proposed an approximately optimal estimator of a common odds ratio for pair-matched case-control studies. His approach is easily extended to general stratified studies. For unmatched stratified studies, the form of the approximately optimal estimator is very simple, and may often correspond to no more than a small correction to the ordinary stratified estimator.