Using your answer to Exercise 13.14 and your knowledge about correlation, how would you

expect the degree of correlation between two variables (sets of data) to affect the magnitude of

the t test between them?

Exercise 13.14

odify the data in Exercise 13.6 by shifting the entries in the “12 hour” column so as to increase

the relationship between the two variables. Run a t test on the modified data and notice the

effect on t. (You could never do this with real data, because paired scores must be kept together,

but doing so here reveals the important role played by the relationship between variables.)

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