Short Answer

A cognitive psychologist tests reaction times under three different lighting conditions (dim, normal, bright) using an ANOVA. The analysis reveals a mean squares between groups (MSBMS_B) of 5,971.88 and a mean squares within groups (MSWMS_W) of 602.23. Calculate the FF statistic using these values (round to two decimal places) and state what this calculated ratio represents in terms of variance estimates.

Question: A cognitive psychologist tests reaction times under three different lighting conditions (dim, normal, bright) using an ANOVA. The analysis reveals a mean squares between groups (MSBMS_B) of 5,971.88 and a mean squares within groups (MSWMS_W) of 602.23. Calculate the FF statistic using these values (round to two decimal places) and state what this calculated ratio represents in terms of variance estimates.

Sample answer: Using the formula F=MSBMSWF = \frac{MS_B}{MS_W}, the calculation is F=5971.88602.239.92F = \frac{5971.88}{602.23} \approx 9.92. This value of 9.92 represents the ratio of the estimate of population variance based on differences between the sample means to the estimate of population variance based on differences within the samples.

Key points:

  • State the calculation: F=5971.88602.23F = \frac{5971.88}{602.23}.
  • Calculate the correct value of F9.92F \approx 9.92.
  • Explain that the calculated FF represents the ratio of between-groups variance estimate to within-groups variance estimate.

Rubric: The student must correctly apply the formula F=MSBMSWF = \frac{MS_B}{MS_W} to calculate F=9.92F = 9.92 (or show the division of 5,971.88 by 602.23) and state that this ratio represents the two distinct estimates of population variance (between-groups vs. within-groups variance).

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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