Do boys who feel that they are "underweight" actually weigh less than boys who feel that they are "about right" in weight? If not, this suggests that boys do not have a good sense of their weight relative to others. The table has a random sample of observations from the Youth At Risk survey, and includes the weights (in kg) of 17 year-old boys. Assume that the distribution of weights in both populations is close to Normal.
a. Test the hypothesis that the mean weight of boys who feel they are 'underweight' is less than the mean weight of boys who are 'about right'. Use a significance level of 0.05.

b. Using only the first five observations in each group, repeat the hypothesis test.
c. Compare the results. Why do the conclusions differ?

Transcribed Image Text:

Under Weight 69 61 74 About Right 68 95 68 86 61 68 0 59 63 79 59 67 61 51 58 57 61 59 65 73 59 57 79 64 67