Question 1:

Hoaglin, Mosteller, and Tukey (1983) present data on blood levels of beta-endorphin as a function of stress; concentration of beta-endorphin is measured using fmol/ml.The researchers took beta-endorphin levels for 19 patients 12 hours before surgery (low stress) and again 10 minutes before surgery (high stress). The data are presented below (Hint: double-check your answers using R).

Patient	12-hrs	10-min
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19	10 6 8 12 5 11 5 3 7 5 4 8 7 15 8 17 15 4 2	6 14 13 18 14 9 18 42 8 6 25 12 52 20 16 15 11 3 2

a) Use a two-tailed test with = .01 to determine whether the beta-endorphin levels changed as a function of stress.

Step 1: Hypotheses:

Step 2: Decision Criterion:

Step 3: Obtain the Statistic[PW1]:

Step 4: Make a Decision:

Step 5: Report the Result:

b) Report and interpret the effect size using Cohen's d.

c) Report and interpret the 95% confidence interval. If we had conducted the original analysis using an alpha level of .05, would it be statistically significant? Explain your answer.

[PW1]If you subtract the 10-min column from the 12-hrs column, the mean difference and their value for t will be negative, as will their computation of d and their confidence interval.