Chapter 6

Exercises: 6.35

Also:

1. In an experiment to determine the effect of a drug on the blood glucose concentration of diabetic rats, six rats were given the drug while five others were used as controls. The blood glucose levels of the treated group (in mg/ml) were 2.02, 1.71, 2.04, 1.50, 1.83, and 1.64; for the controls, the levels were 2.15, 1.92, 1.78, 2.04, and 2.22. Assuming these samples come from normal distributions with the same variance, test the hypothesis that the treatment has no effect on mean blood glucose concentration.
2. In the package ISwR, the data set energy contains data on the energy expenditure in groups of lean and obese women. The first column of energy contains the 24 hour energy expenditure of the women and the second categorizes the women as either lean or obese. Is the mean energy expenditure the same between the two groups? Before performing a two-sample t-test, test whether it is safe to assume the variances of the two samples are the same.
3. In the same package, the data set vitcap contains data on the vital capacity (a measure of lung capacity) for workers in the cadmium industry. The three rows contain the age of the worker, the vital capacity of the worker, and the category of the worker (1 if the worker has been exposed to cadmium for more than 10 years and 3 otherwise). Test if the mean vital capacity is the same in the two groups (after first performing a test to see if it is reasonable to assume the variances are the same in the two groups).