A crossover study was conducted to investigate whether oat bran cereal helps to lower cholesterol in hypercholesterolemic males. Fourteen such individuals were randomly placed on a diet that included either oat bran or corn lakes; 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:

LDL (mmol/l)LDL (mmol/l)SubjectCorn FlakesOat Bran14.613.8426.425.5735.405.8544.544.8053.983.6863.822.9675.014.4184.343.7293.803.49104.563.84115.355.26123.893.73132.251.84144.244.14