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.  

There are 14 observations in the dataset.  The variables are:

corn:  LDL in mmol/l while on corn flake diet
oat:   LDL in mmol/l while on oat bran diet