Planned comparisons are which of the following?

• A. Unplanned post hoc tests
• B. A type of exploratory contrast
• C. Planned contrasts
• D. Sequential Bonferroni tests

Answer: (C)

Planned comparisons are a priori tests of specific hypotheses about group means in an ANOVA. They are contrasts you set up before looking at the data, focusing on a small, theory-driven set of differences (for example, treatment groups vs. control or a linear trend across ordered levels). Because these contrasts are pre-specified, you allocate your Type I error to those tests and often gain more power than if you were to test many differences after the fact. They differ from unplanned post hoc tests, which are exploratory and performed after an omnibus ANOVA to identify any differences, usually with adjustments to control the overall error rate.