To test the effectiveness of an exercise machine, nine subjects used the machine over a period of three months. Their resting pulse rates were measured before they began the program and again after three months of using the exercise machine. The results appear in the following table. Subject: A B C D E F G H I Before: 63 73 75 77 81 89 77 75 73 After: 63 69 69 76 77 81 74 73 74 1. Find the mean. 3. of the sample of differences of pulse rates before and after using the machine. 2. Find the standard deviation, 5 : sd, of the sample of differences of pulse rates before and after using the machine. (Make your answer accurate to two decimal places.) 3. Let u : pd be mean of the (hypothetical) population of the differences in pulse rates of all potential users of the machine before and after three months of use, If we want a 95% condence interval for a, what is the critical value t\" that we should use in the formula 8 :: 75* ~ %7 a) t* = 1.860 b) t* = 1.960 c) t* = 2.262 d) r = 2.306 4. Fill in the blanks below to nd a 95% condence interval for ,u = ,ud. (Make the boundaries of the interval accurate to one decimal place.)