Chapter 4.3, Problem 102E

(a)

To determine

To explain why did the researchers randomly assign the subjects to the diet treatments.

Explanation of Solution

The subjects were randomly assigned to the treatments to make sure that the treatment groups are as similar as possible. This is necessary to be sure that the results of the treatment are due to treatment itself and not due to significantly different groups of subjects. Thus also to make sure that the two treatments groups are as similar as possible.

(b)

To determine

To explain to someone who knows little statistics what “lost significantly more weight” means.

Explanation of Solution

“Lost significantly more weight” means that the subjects in the group of the low carb diet they have lost more weight than the group who were on the low fat diet for the first six months. Thus the group of carb diet lost day by day more weight than the other group in the starting of the study.

(c)

To determine

To explain how this information could be consistent with the fact that weight loss in the two groups was not significantly different.

Explanation of Solution

Significantly different means that the difference in result were so extreme that the difference cannot be caused by chance. Also if the study is deemed statistically significant then there's a very low probability the result could have occurred by chance. But in this study only two kg difference is a that could easily occurred by random variation but it is not significant.