Overview for Power and Sample Size for Paired t

Use Power and Sample Size for Paired t to examine the relationship between power, sample size, and the difference when you want to compare the population means based on paired observations. Use these calculations for the following reasons:

Before you collect data for a paired t-test, to ensure that your test has an adequate sample size to achieve acceptable power
After a paired t-test, to improve the design for the next test

The paired t-test is useful for analyzing the same set of items that were measured under two different conditions, differences in measurements made on the same subject before and after a treatment, or differences between two treatments given to the same subject.

For example, a manager at a fitness facility wants to determine whether a weight-loss program is effective. Before collecting the data for a paired t-test, the manager uses a power and sample size calculation to determine the effect of varying sample sizes on the power function of the test.

Where to find this analysis

To perform a power and sample size calculation for a paired t-test, choose Stat > Power and Sample Size > Paired t.

When to use an alternate analysis

If the observations in your sample are independent and are not matched samples, use Power and Sample Size for 2-Sample t instead. For more information, go to How are dependent and independent samples different?.