One of the primary advantages of a repeated-measures design, compared to independent measures, is that it reduces the overall variability by removing variance caused by individual differences. The following data are from a research study comparing two treatment conditions.
a. Assume that the data are from an independent measures study using two separate samples, each with n = 6 participants. Compute the pooled variance and the estimated standard error for the mean difference.
b. Now assume that the data are from a repeated measures study using the same sample of n = 6 participants in both treatment conditions. Compute the variance for the sample of difference scores and the estimated standard error for the mean difference. (You should find that the repeated measures design substantially reduces the variance and the standard error.)

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Difference Treatment 1 Treatment 2 10 13 3 12 12 8. 10 2 10 6. 1. 2 M = 8 M = 10 Mp = 2 SS = 10 SS = 34 SS = 30