1. **Stating the problem:** We have three groups with an independent variable (IV) having three levels: (1) watch TV, (2) read books, and (3) meet with friends. 2. **Given data:** - SSBcomparison1 (groups (1)+(2) vs. group (3)) = 300 - Total SSB from omnibus ANOVA = 750 3. **Understanding SSB (Sum of Squares Between groups):** SSB measures the variability between group means. 4. **Key property:** The total SSB is the sum of the SSBs of all independent comparisons that partition the groups without overlap. 5. **Since the omnibus SSB = 750, and one comparison (groups (1)+(2) vs. group (3)) accounts for 300, the remaining SSB must come from the other comparison (group (1) vs. group (2)).** 6. **Therefore,** $$\text{SSBcomparison2} = \text{SSB} - \text{SSBcomparison1} = 750 - 300 = 450$$ 7. **Interpretation:** The SSB for comparing group (1) to group (2) is 450. This means the variability between groups (1) and (2) accounts for 450 of the total between-group variability. **Final answer:** $$\boxed{\text{SSBcomparison2} = 450}$$