A crossover study was conducted to investigate whether oat bran cereal helps to

lower serum cholesterol levels in hypercholesterolemic males. Fourteen such

individuals were randomly placed on a diet that included either oat bran or corn flakes;

after two weeks, their low-density lipoprotein (LDL) cholesterol levels were recorded.

Each man was then switched to the alternative diet. After a second two-week period, the

LDL cholesterol level of each individual was again recorded.

The data from this study are shown below.

Subject LDL (mmol/l)

Corn Flakes Oat Bran

1 5.61 3.84

2 5.42 5.57

3 5.40 5.85

4 4.54 4.80

5 3.98 3.68

6 3.82 2.96

7 5.01 3.41

8 4.64 3.72

9 3.80 3.49

10 4.06 3.84

11 5.35 5.26

12 4.89 3.73

13 2.25 1.84

14 4.24 3.34

a. Are the two samples of data paired or independent?

b. What are the appropriate null and alternative hypotheses for a one-sided test?

c. Conduct the test at the 0.05 level of significance. What is the p-value?

d. What do you conclude?