A study was conducted to investigate whether oat bran cereal helps to lower serum cholesterol in men with high cholesterol levels. Fourteen men were placed randomly on a diet that included either oat bran or cornflakes; after two weeks, their low-density lipoprotein (LDL) choles- terol levels were recorded. Each man was then switched to the alternative diet. After a second two-week period, the LDL cholesterol level of each person was recorded again. The data are shown in Table E2.18. Calculate the LDL difference (cornflake-oat bran) for each of the 14 men, then the mean x, variance s2, and standard deviation s for this sample of differences.
LDL (mmol/L)
Subject Cornflakes Oat Bran
1 4.61 3.84
2 6.42 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 4.41
8 4.34 3.72
9 3.80 3.49
10 4.56 3.84
11 5.35 5.26
12 3.89 3.73
13 2.25 1.84
14 4.24 4.14