Use the power curve to help you choose the appropriate sample size or power for your test. This power curve plots the power of the test versus the ratio. Ratio refers to the ratio between the comparison variability and the hypothesized value.

If you provide the ratio that you want to be able to detect and the size of your sample, Minitab will calculate the power of the test.

For the lumber data, the power curve represents every combination of power of a test and the ratio the test can detect based on a sample of size 50. The symbol on the power curve represents the calculated power of 0.773867 for test that can detect a ratio of 0.75.