COMPARISON OF PROCEDURES FOR ESTIMATING SAMPLE NUMBERS

Published standard methods for estimating sample numbers entail hidden tradeoffs. This note will describe the nature of these tradeoffs and their consequences. A modified version of the standard method is prese nted. The modification recognizes that the desired answer is implicit in the t-statistic. The modified version uses a succession of estimate s until achieving convergence. Examples are presented showing that eit her under- or overestimation is possible when using the original metho ds compared with the modified method. The variation in estimates refle cts the variation in the tolerance probability. We recommend when to s elect specific methods.