Question

2) 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 levels? Use a two-tailed test with α = .01. State the null hypothesis and tcritical you will use to evaluate the null hypothesis.

b. Compute Cohen’s d and r2 to evaluate the size of the treatment effect. Conclude with a separate summary statement for each measure of effect size that is appropriate for publication in a scientific journal.

Answer 1