American journal of epidemiology
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Precise measurement of confounding or effect modifying variables is seldom possible. Nondifferential misclassification of such a variable can introduce bias in the odds ratios within the strata of the confounding variable. ⋯ For one stratum, the degree of bias introduced in the odds ratio is dependent only on the sensitivity of the measure of the confounding variable while only the specificity of this measure determines the bias introduced in the other stratum-specific odds ratio. The results are applied to a case-control study of fenoterol prescription and asthma death.