One of the primary advantages of a repeated-measures design, compared to an independent-measures design, is that it reduces the overall variability by removing variance caused by individual differences. The following data are from a research study comparing three treatment conditions.

a. Assume that the data are from an independent measures study using three separate samples, each with n = 6 participants. Ignore the column of P totals and use an independent measures ANOVA with = .05 to test the significance of the mean differences.

b. Now assume that the data are from a repeated measures study using the same sample of n = 6 participants in all three treatment conditions. Use a repeated-measures ANOVA with α = .05 to test the significance of the mean differences.

c. Explain why the two analyses lead to different conclusions.

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Treatment Treatment Treatment 2 3 6. 12 27 8. 24 N = 18 G = 108 5 21 12 EX = 800 4 4 3 5 15 M = 4 M = 6 M = 8 T = 24 T = 36 T = 48 SS = 42 SS = 34 SS = 28