1. In the experiment described in the article "Study Points to Benefits of Knee Replacement Surgery Over Therapy Alone" (The New York Times, October 21, 2015), adults who were considered candidates for knee replacement were followed for one year. Suppose that 200 patients were randomly assigned to one of two groups. One hundred were assigned to a group that had knee replacement surgery followed by therapy and the other half were assigned to a group that did not have surgery but did receive therapy. After one year, 86% of the patients in the surgery group and 68% of the patients in the therapy only group reported pain relief. Use the data to construct and interpret a 95% confidence interval estimate of the difference in the proportion experiencing pain relief for the surgery treatment and this proportion for the therapy treatment.