Cornell Professor of Nutrition David Levitsky recruited students from two large sections of an introductory health course to test the validity of the

“Freshman 15” theory that students gain 15 pounds their first year. 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.

Subject Number Initial Weight Terminal Weight Subject Number Initial Weight Terminal Weight 1 171 168 35 148 150 2 110 111 36 164 165 3 134 136 37 137 138 4 115 119 38 198 201 5 150 155 39 122 124 6 104 106 40 146 146 7 142 148 41 150 151 8 120 124 42 187 192 9 144 148 43 94 96 10 156 154 44 105 105 11 114 114 45 127 130 12 121 123 46 142 144 13 122 126 47 140 143 14 120 115 48 107 107 15 115 118 49 104 105 16 110 113 50 111 112 17 142 146 51 160 162 18 127 127 52 134 134 19 102 105 53 151 151 20 125 125 54 127 130 21 157 158 55 106 108 22 119 126 56 185 188 23 113 114 57 125 128 24 120 128 58 125 126 25 135 139 59 155 158 26 148 150 60 118 120 27 110 112 61 149 150 28 160 163 62 149 149 29 220 224 63 122 121 30 132 133 64 155 158 31 145 147 65 160 161 32 141 141 66 115 119 33 158 160 67 167 170 34 135 134 68 131 131

a) Use a Wilcoxon signed-rank test to test whether these students’ weights changed. State your hypotheses, check conditions, and complete the test (with technology).

b) Would you prefer the nonparametric test, or the paired t-test asked for in Chapter 12? Explain.