In Exercise 12, you thought about how to design a study to see if it's true that students tend to gain weight during their first year in college. Well, Cornell Professor of Nutrition David Levitsky did just that. He recruited students from two large sections of an introductory health course. Although they were volunteers, they appeared to match the rest of the freshman class in terms of demographic variables such as sex and ethnicity. The students were weighed during the first week of the semester, then again 12 weeks later. Based on Professor Levitsky's data, estimate the mean weight gain in first-semester freshmen and comment on the "freshman 15." (Weights are in pounds.)

Subject Initial Terminal Subject Initial Terminal Number Weight Weight Number Weight Weight 21 157 158 22 119 126 113 114 120 128 135 139 26 148 150 110 112 160 163 220 224 132 133 145 147 141 158 160 135 134 148 150 165 138 198 201 122 124 146 146 168 136 115 119 150 155 106 142 148 120 124 9 144 148 156 154 114 121 123 122 126 120 115 115 118 110 113 146 127 105 125 125 134 104 10 114 12 13 32 141 15 35 164 137 142 127 102 37 Subject Initial TminalSubjectInitial Terminal Number Weight Weight Number Weight Weight 150 151 187 192 96 105 105 127 130 142 144 140 143 107 107 104 105 106 108 185 188 125 128 125 126 155 158 60 118 120 150 149 149 63 122 121 155 158 160 161 115 119 167 170 131 131 43 57 58 59 47 48 149 51 52 53 160 162 134 134 15 151 127 130 67