A data set from Oehlert (2000) \emph{A First Course in Design and
Analysis of Experiments}, New York: W. H. Freeman.

Data originally from Khuri, A.~I. (1992).  ``Response surface models
with random block effects.'' {\em Technometrics\/}~{\em 34}, 26--37.

Columns are day, (coded) time and temperature, and strength (psi).