The method to estimate the sample size in stratified two-stage sampling and its application in medical survey *

摘要

In this article, methods of evaluating minimum value in infinitesimal calculus were applied to deduce the formulas for the optimum sample size for stratified two-stage, so as to minimize the cost for specified value of the sampling error and to minimize the sampling error for specified cost. The formulas were employed successfully in the survey of medical cost in Ministry of Railway of China.