A data set from Oehlert (2000) \emph{A First Course in Design and Analysis of Experiments}, New York: W. H. Freeman. Data originally from Rollag, M.~D. (1982). ``Ability of tryptophan derivatives to mimic melatonin's action upon the {S}yrian hamster reproductive system. {\em Life Sciences\/}~{\em 31}, 2699--2707. Testes weight for four groups of 8 hamsters each. Columns are treatment (dose of melatonin daily in nmole), average testes weight (mg), and SD of testes weight (mg).