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

Data originally from Alvin Bussan (1995) "Selection for Weed Competitiveness
among Soybean Genotypes", MS Thesis, Univ. of Minnesota, St. Paul, MN.

Column 1 is location (1 = Rosemount, 2 = St. Paul).
Column 2 is treatment (1 = herbicide 2 weeks after planting, 2 = 
herbicide 4 weeks after planting, 3 = no herbicide).
Column 3 is variety. 1-16 are Parker, Lambert, M89-792,
Sturdy, Ozzie, M89-1743, M89-794, M90-1682, M89-1946,
Archer, M89-642, M90-317, M90-610, M88-250, M89-1006,
M89-1926.
Col 4 is weed biomass in kg/ha.