1. An athletic trainer wishes to study the effectiveness of knee braces in preventing tears of the ACL in college football linemen. Over several years, linemen are randomized into two groups. One group wears the knee brace and the other group (control) wears only the standard protective gear. The linemen are categorized as to whether they experienced a torn ACL. The results of the study are as follows. Knee brace No knee brace Injured ACL A = 5 C=20 25 No injury to ACL B=40 45 D=40 60 80 Total = 105 a. Calculate and interpret the relative risk. b. Calculate and interpret the attributable risk. c. Calculate and interpret the number needed to treat.