A researcher for a cereal company wanted to demonstrate the health benefits of eating oatmeal. A sample of 9 volunteers was obtained and each participant ate a fixed diet without any oatmeal for 30 days. At the end of the 30-day period, cholesterol was measured for each individual. Then the participants began a second 30-day period in which they repeated exactly the same diet except that they added 2 cups of oatmeal each day. After the second 30-day period, cholesterol levels were measured again and the researcher recorded the difference between the two scores for each participant. For this sample, cholesterol scores averaged MD = 16 points lower with the oatmeal diet with SS = 538 for the difference scores.
a. Are the data sufficient to indicate a significant change in cholesterol level? Use a two-tailed test with a = .01.
b. Compute r2, the percentage of variance accounted for by the treatment, to measure the size of the treatment effect.
c. Write a sentence describing the outcome of the hypothesis test and the measure of effect size as it would appear in a research report.