1. A researcher wishes to compare the effect of two stepping heights (low and high) on heartrate in a step-aerobics workout. A collection of 50 adult volunteers was randomly divided into two groups of 25 subjects each. Group 1 did a standard step-aerobics workout at the low height. The mean heartrate at the end of the workout group 1 was 1 = 90.00 beats per minute with a standard deviation s1 = 9 beats per minute. Group 2 did the same workout but at the high step height. The mean heart-rate at the end of the workout for the subjects in group 2 was 2 = 95.08 beats per minute with a standard deviation s2 = 12 beats per minute. Assume the two groups are independent and the data are approximately Normal. Let µ1 and µ2 represent the mean heart rates we would observe for the entire population if all members of this population did the workout using the low or high step height, respectively. Suppose the researcher had wished to test the hypotheses H0: µ1 = µ2, H a: µ1 < µ2. The P-value for the test is (use the conservative value for the degrees of freedom)
A. larger than 0.10.
B. between 0.10 and 0.05.
C. between 0.05 and 0.01.
2. A sportswriter wishes to see if a football filled with helium travels farther, on average, than a football filled with air. To test this theory, the writer uses 18 adult male subjects, randomly divided into two groups of 9 subjects each. Group 1 kicked a football filled with helium to the recommended pressure. Group 2 kicked a football filled with air to the recommended pressure. The mean yardage for group 1 was 1 = 30 yards, with a standard deviation s1 = 8 yards. The mean yardage for group 2 was 2 = 26 yards, with a standard deviation s2 = 6 yards. Assume the two groups of kicks are independent. Let µ1 and µ2 represent the mean yardage observed for the entire population if all members of the population kicked, respectively, a helium- and air-filled football. Assuming two-sample t procedures are safe to use, a 90% confidence interval for µ1 - µ2 is (use the conservative value for the degrees of freedom)
A. 4 ± 5.5 yards.
B. 4 ± 6.2 yards.
C. 4 ± 7.7 yards.