Description
40 rats were given divided randomly into four groups and assigned to one of
four treatments: placebo, drug A, drug B, or both drug A and drug B.
Response is a standard measure of physiological arousal.
Format
A data frame with 40 observations, 10 in each of 4 columns the
  corresponding to placebo, drug A, drug B and both drug A and drug B; no
  NAs.  - Placebo
 - Rats receiving a placebo treatment.
  - Drug.A
 - Rats receiving only drug A.
  - Drug.B
 - Rats receiving only drug B.
  - Drug.A.B
 - Rats receiving both drug A and drug B.
  
Source
Richard Lowry. Concepts & Applications of Inferential Statistics.
  Vassar College, Poughkeepsie, N.Y., 2010,
  http://faculty.vassar.edu/lowry/webtext.html