Whether or not you found a significant difference in Exercise 13.13, Vul and Pashler did. But

are first guesses better than the average of the two?

Exercise 13.13

Assume that the mean and the standard deviation of the difference scores in Exercise 13.6

would remain the same if we added more subjects. How many subjects would we need to

obtain a t that is significant at α = .01 (two-tailed)? (The difference was significant at α = .05, but not at α = .01.) (We will return to this general problem in Chapter 15.)

Exercise 13.6

Hoaglin, Mosteller, and Tukey (1983) present data on blood levels of beta-endorphin as a

function of stress. They took beta-endorphin levels for 19 patients 12 hours before surgery and

again 10 minutes before surgery. The data are presented on the next page, in fmol/ml:

Transcribed Image Text:

Subject 12 Hours Before 10 Minutes Before -234567 10.0 6.5 6.5 14.0 8.0 13.5 12.0 18.0 5.0 14.5 11.5 9.0 5.0 18.0 8 3.5 42.0 9 7.5 7.5 10 5.8 6.0 || 4.7 25.0 12 8.0 12.0 13 7.0 52.0 14 17.0 20.0 15 8.8 16.0 16 17.0 15.0 17 15.0 11.5 18 4.4 25 19 2.0 20