1. Is there a statistically significant difference between standard deviations of blood polyphenol level change in the red and white wine groups in Exercise 17.7?
Observational studies suggest that moderate use of alcohol reduces heart attacks, and that red wine may have special benefits. One reason may be that red wine contains polyphenols, substances that do good things to cholesterol in the blood and so may reduce the risk of heart attacks. In an experiment, healthy men were assigned at random to drink half a bottle of either red or white wine each day for two weeks. The level of polyphenols in their blood was measured before and after the two week period. Here are the percent changes in level for the subjects in both groups.
Red Wine 3.5 8.1 7.4 4.0 0.7 4.9 8.4 7.0 5.5
White Wine 3.1 0.5 -3.8 4.1 -0.6 2.7 1.9 -5.9 0.1
2. "The phenomenon of road rage had been frequently discussed but infrequently examined". So begins a report based on interviews with randomly selected drivers. The respondent's answers to interview questions produced scores on an "angry/threatening driving scale" with values between 0 and 19. Here are summaries of the scores:
Group n x bar s
Male 596 1.78 2.79
Female 769 0.97 1.84
a) We suspect that men are more susceptible to road rage than women. Carry out a test of that hypothesis. (State hypothesis, find the test statistic and P-value, and state your conclusion.
b) The subjects were selected using random digit dialing. The large sample sizes make the Normality condition unnecessary. There is one aspect of the data production that might reduce the validity of the data. What is it?
Solution contains various testing of hypothesis problems concerning testing the equality of variance, t-test etc.