One treatment for multiple myeloma (cancer of the blood and bones) is a stem cell transplant. However, in some cases the cancer returns. McCarthy and colleagues reported on a study that randomly assigned 460 patients (100 days after a stem cell transplant) to receive either lenalidomide or placebo. At one point in the study, 46 of the patients who received the real drug had a bad result (had progressive disease or had died), compared to 101 of those who received the placebo. Assume that exactly half were assigned to each group.
a. Find and compare the percentages that had a bad result for the two groups.
b. Test the hypothesis that the drug reduced the chance of a bad result compared to the placebo using a significance level of 0.05.
c. The study started in April 2005 and was "unblinded" in 2009 when an interim analysis showed better results with the group taking the drug. After the unblinding, many of the patients from the placebo group "crossed over" to the drug group. Explain what you think "unblinding" means and why this seems like a reasonable thing to do.