Researchers Wilt et al. (New England Journal of Medicine, 2012) investigated whether surgery, compared to just observation, was (more) effective in improving men's survival chances after being diagnosed with prostate cancer. The researchers identified 731 men with localized prostate cancer who volunteered to participate. They randomly assigned 364 men to surgery and the remaining 367 to observation. All participants were followed for about 10 years. In those 10 years, 21 surgery recipients died of prostate cancer-related reasons compared to 31 observation recipients.

a) Write the null and alternative hypotheses in words and in symbols

b) Set up a two-way contingency table

c) Calculate and interpret the relative risk

d) Calculate a 95% confidence interval and interpret it.

e) Calculate a standardized statistic for these data and hypotheses. Show work.

f) Make a decision in regard to the null hypothesis (use either the confidence interval or the standardized statistic). WHY did you make your decision?

g) Make a conclusion.

1. In a survey of introductory statistics students, an instructor asked her students to report how many Facebook friends they had. Suppose that the intent is to study whether there is an association between number of Facebook friends and a person's sex.

Here are a few summary statistics about the data: