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A research team rejects the null hypothesis in a one-way ANOVA comparing five types of therapy. They debate whether to report just the ANOVA results or to also conduct and report post hoc comparisons. Evaluate the necessity of conducting post hoc comparisons in this scenario and state why reporting only the ANOVA results would be statistically incomplete.
Question: A research team rejects the null hypothesis in a one-way ANOVA comparing five types of therapy. They debate whether to report just the ANOVA results or to also conduct and report post hoc comparisons. Evaluate the necessity of conducting post hoc comparisons in this scenario and state why reporting only the ANOVA results would be statistically incomplete.
Sample answer: Conducting post hoc comparisons is necessary because the rejected null hypothesis only indicates that at least one difference exists among the five therapy groups, but does not specify where. Reporting only the ANOVA results is incomplete because it fails to pinpoint exactly which selected pairs of group means are significantly different from each other, leaving the specific effects of the therapies unclear.
Key points:
- Post hoc comparisons are necessary to follow up a significant one-way ANOVA.
- ANOVA results alone are incomplete because they do not specify which means differ.
- Post hoc comparisons pinpoint the exact differences between selected pairs of group means.
Rubric: The answer must evaluate post hoc comparisons as necessary and explain that the ANOVA alone is incomplete because it doesn't specify which groups differ.
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Research Methods in Psychology - 4th American Edition @ KPU
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