Modelling covariance: The milk protein data

  Following Example 5.1 of Diggle et al. (1994), we develop a parametric model for the covariance structure of the milk protein data.

The dataset milk.dat consists of weekly measurements of the protein content of milk samples from each of 79 cows randomly allocated to three different diets: barley, a barley and lupins mixture, and barley alone. The goal is to determine whether (and if so, how) diet affects milk protein. Measurements were taken in the weeks following calving for each cow, but as the experiment terminated at a fixed date not all cows had the same number of measurements taken.