In Exercise 7.25, data from Everitt showed that girls receiving cognitive behavior therapy gained weight over the course of the therapy. However, it is possible they just gained weight because they just got older. One way to control for this is to look at the amount of weight gained by the cognitive therapy group (n 5 29) in contrast with the amount gained by girls in the Control group (n 5 26) who received no therapy. The data on weight gain for the two groups is shown below.

Control CognitiveTherapy

–0.5 3.3 1.7 –9.1

–9.3 11.3 0.7 2.1

–5.4 0.0 –0.1 –1.4 12.3 –1.0 –0.7 1.4

–2.0 –10.6 –3.5 –0.3

–10.2 –4.6 14.9 –3.7

–12.2 –6.7 3.5 –0.8 11.6 2.8 17.1 2.4

–7.1 0.3 –7.6 12.6 6.2 1.8 1.6 1.9

–0.2 3.7 11.7 3.9

–9.2 15.9 6.1 0.1 8.3 –10.2 1.1 15.4

–4.0 –0.7 20.9 Mean –0.45 3.01 St Dev. 7.99 7.31 Variance 63.82 53.41 Run the appropriate test to compare the group means. What would you conclude?