A data set from Oehlert (2000) \emph{A First Course in Design and Analysis of Experiments}, New York: W. H. Freeman. Data originally from Lynch, S.~M. and J.~J. Strain (1990). ``Effects of skimmed milk powder, whey or casein on tissue trace elements status and antioxidant enzyme activites in rats fed control and copper-deficient diets.'' {\em Nutrition Research\/}~{\em 10}, 449--460. Table of treatment means. Columns are Cu normal or deficient; rows are skim milk protein, whey, and casein. Response is iron level (mg/g) in liver tissue.