Free Response Question
In a study of the effectiveness of weight-loss programs, 47 subjects who were at least 20% overweight took part in a group support program for 10 weeks. Private weighings determined each subject’s weight at the beginning of the program and 6 months after the program’s end. The matched pairs t test was used to assess the significance of the average weight loss. The paper reporting the study said, “The subjects lost a significant amount of weight over time, t(46) = 4.68, P < 0.01.”
a)Why was the matched-pairs t statistic appropriate?
b).Explain to someone who knows no statistics but is interested in weight-loss programs what the practical conclusion is.
c).The paper follows the tradition of reporting significance only at fixed levels such as = 0.01. In fact the results are more significant than “P < 0.01” suggests. What can you say about the P-value of the t test?