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Explain why the psychologist cannot use a standard tt-test to analyze these results, and explain how the analysis of variance (ANOVA) solves this limitation in the context of this study.

Case context: A psychologist is investigating the effect of three different sleep environments on cognitive performance: a completely silent room, a room with white noise, and a room with background music. The psychologist plans to compare the mean cognitive performance scores across these three distinct conditions.

Question: Explain why the psychologist cannot use a standard tt-test to analyze these results, and explain how the analysis of variance (ANOVA) solves this limitation in the context of this study.

Sample answer: A standard tt-test is inappropriate because it is strictly limited to evaluating differences between exactly two means. Since this study compares the means of three different sleep environments (which is more than two conditions), the psychologist must use the analysis of variance (ANOVA). ANOVA serves as a necessary extension of the tt-test specifically designed to evaluate and compare the means of more than two groups or conditions.

Key points:

  • The study has three groups, which is more than the two-mean limit of the tt-test.
  • The standard tt-test is strictly limited to evaluating differences between exactly two means.
  • ANOVA solves this by allowing the comparison of more than two means.

Rubric: The response must explain that the study has three conditions (more than two means), identify the tt-test limitation (only compares exactly two means), and explain how ANOVA resolves this by allowing comparisons of more than two means.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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