Waist-to-hip ratio was measured on 8 men just before they entered a weight loss program (time 1) and again 6 months after the program (time 2). The results are below.
Subject 1 2 3 4 5 6 7 8
Time 1 1.03 0.99 1.18 0.82 1.02 1.05 1.06 0.82
Time 2 1.00 1.02 1.12 0.78 1.06 1.00 1.08 0.76
data one;
input WHR1 WHR2;
diff = WHR1 - WHR2;
Datalines;
1.03 1.00
0.99 1.02
1.18 1.12
0.82 0.78
1.02 1.06
1.05 1.00
1.06 1.08
0.82 0.76
;
run;
a. Calculate the difference for each subject (as time 1 value minus time 2 value), then calculate the mean and standard deviation of these differences. You can do this however you like.
b. Using the information from part (a), "by hand", calculate a 90% confidence interval for the difference of the means for the two time periods (i.e., for the mean difference).
c. We want to use a paired t-test, at a = .05, to test if the mean waist-to-hip ratio is smaller at time 2 than at time 1 (i.e., test if the program is effective). Use PROC TTEST to obtain the test statistic and p-value. Turn in the printout.
d. A colleague looks at the printout and decides that we have proven that the program is not effective. Do you agree with his conclusion? Why or why not?