Use Power and
Sample Size for 1-Sample Z to examine the relationship between power, sample size, and the difference when you want to compare the mean of a population to a target or reference value. These calculations require you to know the standard deviation of the population. Use these calculations for the following reasons:

- Before you collect data for a 1-sample Z test, to ensure that your test has an adequate sample size to achieve acceptable power
- After a 1-sample Z-test, to improve the design for the next test

For example, a quality analyst wants to determine whether the mean thread length of bolts meets the target of 20mm. Before collecting the data for a 1-sample Z test, the analyst uses a power and sample size calculation to determine how large the sample must be to obtain a power of 80% (0.8).

To perform a power and sample size calculation for a 1-Sample Z-test, choose

.If you do not know the standard deviation of the population, use Power and Sample Size for 1-Sample t.