A pharmaceutical company tested three
formulations of a pain relief medicine for migraine headache
sufferers. For the experiment, 27 volunteers were
selected and 9 were randomly assigned to one of three
drug formulations. The subjects were instructed to take
the drug during their next migraine headache episode and
to report their pain on a scale of 1 = no pain to 10 =
extreme pain 30 minutes after taking the drug.