Use Power and Sample Size for 1 Proportion to examine the relationship between power, sample size, and the comparison proportion when you want to compare the proportion of a population to a target or reference value. These calculations require that your data contain only two categories, such as pass/fail. Use these calculations for the following reasons:

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

For example, a marketing analyst wants to determine whether mailed advertisements that were sent to a random sample of households result in a response rate that is different from the national average of 6.5% (target value). Before collecting the data for a 1 proportion test, the analyst uses a power and sample size calculation to determine what the power of the test will be with different sample sizes.

To perform a power and sample size calculation for a 1 proportion test, choose

.If your data contain counts, such as the number of defects per unit, use Power and Sample Size for 1-Sample Poisson Rate. For more information on data types, go to Data types you can analyze with a hypothesis test.