Researchers Vogel et al. (JAMA, 2006) reported the following findings about the Study of Tamoxifen and Raloxifene (STAR), a study involving postmenopausal women who were at an increased risk for invasive breast cancer. Of the 9,726 women randomly assigned to use tamoxifen daily, 163 developed invasive breast cancer sometime during the next five years, compared to 168 in the group of 9,745 who were randomly assigned to use raloxifene daily.

a. Is this an experiment or an observational study? Explain how you are deciding.

b. Identify the explanatory and response variables. Also, identify whether each is categorical or quantitative.

c. Organize the counts in a well-labeled 2 2 table.

d. Find the observed difference in proportion of breast cancer cases between the tamoxifen and raloxifene users.

e. State the appropriate null and alternative hypotheses in words.

f. Explain why it would be okay to use the theory-based method (that is, normal distribution based method) to find a p-value for this study.

g. Use an appropriate applet to find and report the following from the data. The standardized statistic The theory-based p-value

h. State a complete conclusion about this study, including significance, estimation (confidence interval), causation, and generalization. Be sure to explain how you are arriving at your conclusion.