For each of the following studies using difference scores, test the significance using a ttest for dependent means.
Number of Difference Scores in Sample Mean of Difference Scores in Sample Estimated Population Variance of Difference Scores Tails Significance Level
(a) 20 1.7 8.29 1 (high predicted) .05
(b) 164 2.3 414.53 2 .05
(c) 15 –2.2 4.00 1 (low predicted) .01
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