Design and Sensitivity Evaluation of Follow-Up Studies for Risk Factor Assessment

In follow-up studies of samples from human populations, a major goal is frequently the assessment of association of risk factors with some disease outcome. For a completed study it seems of interest to quantify the sensitivity of the study, that is, to prescribe the intensity of association which the study would be able to detect with high probability. On the other hand, it is of interest to determine the size of the cohort and the length of follow-up needed to give a high probability of detecting an association of a given intensity. A basis for answering these questions is provided under the assumptions of underlying joint normality of distribution of risk factors, a Hotelling's T test of equality of risk factors among cases and noncases, and a probit plane in the risk factors as a risk-function model.