The Effect of Vitamin C on Tooth Growth in Guinea Pigs
Usage
data(pigs)
Format
A data frame with 60 observations on 3 variables.
  | [,1]   |    len    |    numeric   |    Tooth length | 
  |  [,2]   |    supp   |    factor    |    Supplement (VC or OJ). | 
  |  [,3]   |    dose   |    numeric   |    Dose in milligrams.  | 
Description
The response is the average length of odontoblasts (teeth) in
each of 10 guinea pigs.  Three dose levels 0.5, 1, and 2 mg
of juice and acid in the juice were used.
This makes no sense - check the original source.
Source
C. I. Bliss (1952).  The Statistics of Bioassay, Academic Press.References
McNeil, D. R. (1977).  Interactive Data Analysis.  New York: Wiley.