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

Data originally from Atsushi Tajima (1987) "Some Aspects of Preserving
Chicken Semen: Glycerol Effect, Assay Method, and Application"
Ph. D. Dissertation, Univ. of Minnesota, St. Paul, MN.

Four semen mixtures are prepared, consisting of either
fresh or frozen Rhode Island Red semen, and either fresh or
frozen White Leghorn semen.  Batches of Rhode Island Red hens
are inseminated and the response measured is the fraction of
the hatching eggs that have white feathers (ie, have the dominant
White Leghorn gene from the semen).  There are 4 replicates.
The data have three columns: response, rir, and wl.  The
response in column 1 is the fraction of hatching eggs with
white feathers.  Column 2 is 1 for fresh RIR semen and 2 for
frozen RIR.  Column 3 is 1 for fresh WL semen, and 2 for frozen
WL semen.