In exercises that call for two-sample procedures, you may use either of the two approximations for the degrees of freedom that we have discussed: the value given by your software or the smaller of and . Be sure to state clearly which approximation you have used.
7.64 Study design matters!
In the previous exercise, you analyzed data on the ego strength of high-fitness and low-fitness participants in a campus fitness program. Suppose that instead you had data on the ego strengths of the same men before and after six months in the program. You wonder if the program has affected their ego scores. Explain carefully how the statistical procedures you would use would differ from those you applied in Exercise 7.63.