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

Data originally from Amoah, F.~M., K.~Osei-Bonsu, and F.~K. Oppong (1997).
``Response of improved robusta coffee to location and management practices
in {G}hana.'' {\em Experimental Agriculture\/}~{\em 33}, 103--111.

Columns are treatment (185, 90, 70, 0 trees per hectare),) location,
and yield (kg/ha).