Professor Gill has taught General Psychology for many years. During the semester, she gives three multiple-choice exams, each worth 100 points. At the end of the course, Dr. Gill gives a comprehensive final worth 200 points. Let x, X,, and x, represent a student's scores on exams 1, 2, and 3, respectively. Let x, represent the student's score on the final exam. Last semester Dr. Gill had 25 students in her class. The student exam scores are shown below. * 1 X 7 X3 Xa 73 80 75 152 93 88 93 185 89 91 90 180 96 98 100 196 73 66 70 142 53 46 55 101 74 77 149 56 60 115 79 90 175 70 88 164 73 141 74 141 184 152 78 148 96 192 68 147 93 183 92 86 177 83 77 159 86 90 177 82 89 175 85 175 71 149 95 192 Since Professor Gill has not changed the course much from last semester to the present semester, the preceding data should be useful for constructing a regression model that describes this semester as well. (a) Generate summary statistics, Including the mean and standard deviation of each variable. Compute the coefficient of variation for each variable. (Use 2 decimal places.) CV X1 % % % % Relative to its mean, would you say that each exam had about the same spread of scores? Most professors do not wish to give an exam that is extremely easy or extremely hard. Would you say that all of the exams were about the same level of difficulty? Consider both means and spread of test scores.) No, the spread is different; Yes, the tests are about the same level of difficulty. Yes, the spread is about the same; Yes, the tests are about the same level of difficulty. Yes, the spread Is about the same; No, the tests have different levels of difficulty. No, the spread is different; No, the tests have different levels of difficulty. (b) For each pair of variables, generate the correlation coefficient r. Compute the corresponding coefficient of determination . (Use 3 decimal places.) *11X2 X1X3 X21 X3 X21 X4 X31 X4