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A researcher is finalizing an ANOVA table for a study comparing three groups with a total of 21 participants. The table lists a between-groups sum of squares (SSbetweenSS_{between}) of 40 and a within-groups sum of squares (SSwithinSS_{within}) of 90. Given that the degrees of freedom are dfbetween=2df_{between} = 2 and dfwithin=18df_{within} = 18, show the calculations to find the mean squares (MSMS) and the calculated FF statistic to complete these empty sections of the table.

Question: A researcher is finalizing an ANOVA table for a study comparing three groups with a total of 21 participants. The table lists a between-groups sum of squares (SSbetweenSS_{between}) of 40 and a within-groups sum of squares (SSwithinSS_{within}) of 90. Given that the degrees of freedom are dfbetween=2df_{between} = 2 and dfwithin=18df_{within} = 18, show the calculations to find the mean squares (MSMS) and the calculated FF statistic to complete these empty sections of the table.

Sample answer: To find the mean squares, divide each sum of squares by its corresponding degrees of freedom: MSbetween=SSbetween/dfbetween=40/2=20MS_{between} = SS_{between} / df_{between} = 40 / 2 = 20 and MSwithin=SSwithin/dfwithin=90/18=5MS_{within} = SS_{within} / df_{within} = 90 / 18 = 5. To find the calculated FF statistic, take the ratio of these mean squares: F=MSbetween/MSwithin=20/5=4F = MS_{between} / MS_{within} = 20 / 5 = 4. Therefore, the researcher should enter MSbetween=20MS_{between} = 20, MSwithin=5MS_{within} = 5, and F=4F = 4 in the table.

Key points:

  • Calculates MSbetweenMS_{between} correctly as 40/2=2040 / 2 = 20.
  • Calculates MSwithinMS_{within} correctly as 90/18=590 / 18 = 5.
  • Calculates the calculated FF statistic correctly as 20/5=420 / 5 = 4.

Feedback: First, calculate the mean squares by dividing the sum of squares by the degrees of freedom: MSbetween=40/2=20MS_{between} = 40 / 2 = 20 and MSwithin=90/18=5MS_{within} = 90 / 18 = 5. Next, calculate the FF statistic by dividing the between-groups mean square by the within-groups mean square: F=20/5=4F = 20 / 5 = 4.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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