If you provide values for power and sample size, Minitab calculates the value of the difference. If you provide values for power and difference, Minitab calculates the value of the sample size.
Minitab uses an iterative algorithm with the power equation. At each iteration, Minitab evaluates the power for a trial sample size or trial difference value, and stops when the power function equals a target power value.
Minitab solves directly for the value you request with the following equations:
Target power and actual power
When Minitab calculates sample size, it may find that no integer value of sample size yields your target power. In such cases, Minitab displays the target value for power alongside the actual power. Actual power is a value corresponding to an integer sample size, and which is nearest to, yet greater than, the target value.
| n ||sample size|
| σ ||standard deviation|
| zα ||one-sided critical value (upper α point of the standard normal distribution)|
| α ||significance level|
| zβ ||upper β point of the standard normal distribution|
| β ||1 – power|
| δ ||difference between the population mean and the hypothesized mean|