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 us determine how large a sample should be. It covers basic examples of three commonly used tests: t-test, χ2 test and analysis of variance. It presents several graphs which can be used to obtain important critical values, such as required sample size for a particular task, and the power (or ability) of a chosen statistical test to actually determine the task required of it.