A data set from Oehlert (2000) \emph{A First Course in Design and Analysis of Experiments}, New York: W. H. Freeman. Data originally from Cochran, W.~G., K.~M. Autrey, and C.~Y. Cannon (1941). ``A double change-over design for dairy cattle feeding experiments.'' {\em Journal of Dairy Science\/}~{\em 24}, 937--951. Columns are cow, period, treatment (1--roughage, 2--limited grain, 3--full grain), and milk production in pounds per six week period.