A person's muscle mass is expected to decrease with age. To explore this relationship
in women, a nutritionist randomly selected 16 women from each 10-year age group,
beginning with age 40 and ending with age 79. The variables include X = age and Y
= measure of muscle mass.
a) Fit and report the results for the following regression model:
Y, = Bo + ß Xi + ß2 X7, +
b) Does the quadratic regression function appear to be a good fit here? Find R2.
Conduct an overall F-test of the model using a-0.05. State the alternatives,
decision rule, and conclusion.
c) Estimate the mean muscle mass for women aged 48 years by reporting a 95%
confidence interval. Interpret your interval.
d) Predict the muscle mass for a woman whose age is 48 years by reporting a 95%
prediction interval. Interpret your interval.
Test whether the quadratic term can be dropped from the regression model; use a- 0.05.
State the alternatives, decision rule, and conclusion.
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