In one-way ANOVA, a larger SS_between / SStotal indicates what about the effect?

• A. A larger effect size
• B. A smaller effect size
• C. No effect
• D. An interaction effect

Answer: (A)

A larger SS_between / SStotal means a larger portion of the total variance is due to differences between the groups, i.e., a larger effect size. SS_between captures how much the group means differ from the overall mean, while SStotal is the total variability in all data. When the group means differ a lot, SS_between becomes big relative to SStotal, pushing the ratio up and signaling a stronger effect of the group factor. If there’s little to no difference between groups, SS_between is small and the ratio shrinks toward zero, indicating a negligible effect. In a one-way design, this ratio essentially reflects how much of the total variance is explained by the grouping, so a larger value clearly points to a bigger effect.