Printed In USA Optimizing Power in Allocating Resources to Exposure Assessment in an Epidemiologic Study

We consider an epidemiologic study with a fixed budget, in which resources may be put into increasing sample size or into improving accuracy of exposure assessments. To maximize study power (efficiency), improving accuracy is preferable if and only if the proportional increase in the square of the validity coefficient is more than the proportional increase in total study costs per subject that is required to achieve it. (The validity coefficient is the correlation between the true exposure and the approximate assessment in the study base.) This is most likely to be so if the cost of exposure measurement remains a small proportion of the overall costs per subject. The design with maximum power will not generally have minimum bias in measure of effect, so that alternative optimally criteria are required if this bias is important. Am J Epidemiol 1996;144:192-7. statistics Improving the accuracy of exposure measurement in an epidemiologic study will in general improve study power and the accuracy of the estimate of the effect of the exposure. However, improving measurement ac-curacy usually requires resources that could be used in other ways, in particular to improve other study in