Choose one of the five types of power analysis available

In Step 2, the Type of power analysis menu in the center of the main window is used to choose the appropriate analysis type.

Example

The first item from the Type of power analysis menu will display input and output parameters appropriate for an a priori power analysis (for t tests for independent groups if you followed the example provided in Step 1).

In an a priori power analyses, sample size N is computed as a function of

• the required power level (1-β),
• the pre-specified significance level α, and
• the population effect size to be detected with probability (1-β).

In a criterion power analyses, α (and the associated decision criterion) is computed as a function of

• 1-β,
• the effect size, and
• a given sample size.

In a compromise power analysis both α and 1-β are computed as functions of

• the effect size,
• N, and
• an error probability ratio q = β/α.

In a post-hoc power analyses the power (1-β) is computed as a function of

• α,
• the population effect size parameter, and
• the sample size(s) used in a study.

In a sensitivity power analyses the critical population effect size is computed as a function of

• α,
• 1-β, and
• N.