99 How do you choose to argue? Refer to the Thinking and Reasoning (Oct. 2006) study of the cognitive skills required for successful arguments, presented in Exercise 23.

Recall that 52 psychology graduate students were equally divided into two groups. Group 1 was presented with arguments that always attempted to strengthen the favored position. Group 2 was presented with arguments that always attempted to weaken the nonfavored position.
Summary statistics for the student ratings of the arguments are reproduced in the accompanying table. In Exercise 23, you compared the mean ratings for the two groups with a small-sample t -test, assuming equal variances. Determine the validity of this assumption at a = .05 .

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Group 1 (support favored position) Group 2 (weaken opposing position) Sample size 26 Mean 28.6 Standard deviation 12.5 26 24.9 12.2 Based on Kuhn, D., and Udell, W. "Coordinating own and other perspectives in argument." Thinking and Reasoning, October 2006.