102. Do diets work? Dr. Linda Stern and her colleagues recruited 132 obese adults at the Philadelphia
Veterans Affairs Medical Center in Pennsylvania
Half the participants were randomly assigned to a
low-carbohydrate diet and the other half to a low-fat
diet. Researchers measured each 拷貝participant's change
in weight and cholesterol level after six months and
again after one year. Subjects in the low-carb diet
group lost significantly more weight than subjects in
the low-fat diet group during the first six months. At
the end of a year, however, the average weight loss
for subjects in the two groups was not significantly
different
(a) Why did researchers randomly assign the subjects to
the diet treatments?
(b) Explain to someone who knows little statistics what
"lost significantly more weight” means.
(e) The subjects in the low-carb diet group lost an average
of 5.1 kg in a year. The subjects in the low-fat diet
group lost an average of 3.1 kg in a year. Explain how
this information could be consistent with the fact that
weight loss in the two groups was not significantly
different
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