How large should my sample be? Some quick guides to sample size and the power of tests

This article provides a simple explanation of how power analysis can help u s determine how large a sample should be. It covers basic examples of three commonly used tests: t-test, chi(2) test and analysis of variance. It pres ents several graphs which can be used to obtain important critical values, such as required sample size for a particular task, and the power (or abili ty) of a chosen statistical test to actually determine the task required of it. (C) 1999 Elsevier Science Ltd. All rights reserved.