Essay

A cognitive psychologist wants to apply a repeated-measures design instead of a between-subjects design to test the impact of three different noise environments on learning. Explain how the application of this design choice alters the mathematical calculation of the within-groups variance (MSWMS_W) and the FF-ratio compared to a one-way ANOVA. Refer to the behavior of participant variance in your explanation.

Question: A cognitive psychologist wants to apply a repeated-measures design instead of a between-subjects design to test the impact of three different noise environments on learning. Explain how the application of this design choice alters the mathematical calculation of the within-groups variance (MSWMS_W) and the FF-ratio compared to a one-way ANOVA. Refer to the behavior of participant variance in your explanation.

Sample answer: In a repeated-measures design, the same participants are tested across all noise conditions, which allows the researcher to measure stable individual differences and subtract them from the within-groups variance (MSWMS_W). Conversely, in a between-subjects design analyzed with a one-way ANOVA, these stable individual differences cannot be isolated and instead inflate the value of MSWMS_W. Mathematically, subtracting these differences in the repeated-measures ANOVA reduces MSWMS_W, which serves as the denominator for the FF-ratio, thereby yielding a higher FF-ratio and a more sensitive statistical test.

Key points:

  • Repeated-measures designs test the same participants, whereas between-subjects designs use separate groups.
  • Stable individual differences are subtracted from the within-groups variance (MSWMS_W) in repeated-measures ANOVA.
  • In a one-way ANOVA, stable individual differences inflate MSWMS_W.
  • Subtracting individual differences lowers MSWMS_W, resulting in a higher FF-ratio and a more sensitive test.

Rubric: Grading Rubric: - 1 point: Explains that repeated-measures design uses the same participants, allowing stable individual differences to be measured and subtracted from MSWMS_W. - 1 point: Explains that in a between-subjects one-way ANOVA, individual differences are not subtracted and instead inflate MSWMS_W. - 1 point: Links the reduction in MSWMS_W to an increased FF-ratio (since MSWMS_W is the denominator) and a more sensitive test.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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