A researcher for a cereal company wanted to demonstrate the health benefits of e

Question

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 average M = 16 points lower with the oatmeal diet with SS = 538 for the difference scores.

1. Are the data sufficient to indicate a significant change in cholesterol level? Use a two-tailed test with = .01.

2. Compute r2 to measure the size of the treatment effect.

Explanation / Answer

1. Using a 2 tailed test

SS = 538, therefore, The t value' = sqrt(SS)/n = sqrt(538)/9 = 2.57

This for a given DF corresponds to a probability score > 0.01/2 [ Since it' a 2 tailed test alpha is 0.01/2]

Therfore, data is not sufficient to indicate a signicficant change in cholestrol level

2) R sqaure = 1- ( Sum of squares Error)/ Sum of squares Total) = 1- (162/ 538) = 0.524

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