A researcher wants to determine whether or not a five-week crash diet is effective over a long period of time. A random sample of 15 dieters is selected.

Each person’s weight is recorded before starting the diet and one year after it is concluded. Based on the data shown at right (weight in pounds), can we conclude that the diet has a long-term effect, that is, that dieters manage to not regain the weight they lose? Include appropriate statistical evidence to justify your answer.

1 2 3 4 5 6 7 8 Before 158 185 176 172 164 234 258 200 After 163 182 188 150 161 220 235 191 9 10 11 12 13 14 15 Before 228 246 198 221 236 255 231 After 228 237 209 220 222 268 234