If a repeatedmeasures study shows a significant difference b

If a repeated-measures study shows a significant difference between two treatments with a = .01, then you can be sure that ____.

Solution

Answers b and c are both incorrect because r² refers to the amount of variance in one variable that is explained by the other in a Pearson correlation. It has nothing to do with a repeated measures study which uses t.

Answer d is correct. When a test is significant at ?=.01, this is only a matter of probability, saying that there is a 1% chance that concluding the two scores are different will be an error. Cohen\'s d is used to measure effect size, and answers a different question than the level of significance, so they may not be in agreement.