2.68  2.36 1916
  2.60  2.41 1917
  2.43  2.39 1918
  2.90  2.85 1919
  2.94  2.82 1920
  2.70  2.73 1921
  2.68  2.58 1922
  2.98  2.89 1923
  2.85  2.78 1924

StrainB Strain13
Average litter size in guinea pigs in 9 successive years.
Box 10.3 Sokal and Rohlf  Biostatistics 1987
Box 13.9 Sokal and Rohlf  Biometry 1981
Box 13.11 Sokal and Rohlf  Biometry 1995
Box 13.12 Sokal and Rohlf Biometry 2012

Data from Sewall Wright, at Harvard University.
Guinea pigs require fresh vegetables. The cost of
vegetables rose in the US during World War I, 1914-1918.
World War I was a period of stress for wright's Guinea
pig colony (pers.comm.  R.R. Sokal, graduate student with Wright).

MTB> read 'gpig.dat' into c1 c2 c3;
SUBC> nobs = 9.
MTB> name c1 'strain B' c2 'strain 13' c3 'year'