In a factorial design, which effect describes the influence of a single factor across all levels of other factors?

In a factorial design, which effect describes the influence of a single factor across all levels of other factors?

• A. Main effect
• B. Interaction effect
• C. Simple effect
• D. Post-hoc effect

Answer: (A)

Think about how a factorial design parses out what each factor contributes on average across all combinations. The main effect is the overall influence of one factor when averaged over the levels of the other factors. It tells you, on average, how changing that factor changes the outcome, without regard to specific interactions with other factors. An interaction effect would indicate that the factor's influence depends on which level the other factor is at, so you can't summarize it with a single average across all levels. A simple effect looks at the factor's impact at a particular level of the other factor, which is more specific than the broad main effect. A post-hoc effect isn't a standard effect type; post-hoc tests are follow-up comparisons after you find significant effects, used to explore where differences lie. Thus, the description matches the main effect.

Think about how a factorial design parses out what each factor contributes on average across all combinations. The main effect is the overall influence of one factor when averaged over the levels of the other factors. It tells you, on average, how changing that factor changes the outcome, without regard to specific interactions with other factors. An interaction effect would indicate that the factor's influence depends on which level the other factor is at, so you can't summarize it with a single average across all levels. A simple effect looks at the factor's impact at a particular level of the other factor, which is more specific than the broad main effect. A post-hoc effect isn't a standard effect type; post-hoc tests are follow-up comparisons after you find significant effects, used to explore where differences lie. Thus, the description matches the main effect.