There has been debate among doctors over whether surgery can prolong life among men suffering from prostate cancer, a type of cancer that typically develops and spreads very slowly. Recently, The New England Journal of Medicine published results of some Scandinavian research. Men diagnosed with prostate cancer were randomly assigned to either undergo surgery or not. Among the 347 men who had surgery, 16 eventually died of prostate cancer, compared with 31 of the 348 men who did not have surgery.
a) Was this an experiment or an observational study? Explain.
b) Create a 95% confidence interval for the difference in rates of death for the two groups of men.
c) Based on your confidence interval, is there evidence that surgery may be effective in preventing death from prostate cancer? Explain.