Consider the clinical trial outlined above in which three competing treatments for joint pain

are compared in terms of their mean time to pain relief in patients with osteoarthritis.

Because investigators hypothesize that there may be a difference in time to pain relief in

men versus women, they randomly assign 15 participating men to one of the three

competing treatments and randomly assign 15 participating women to one of the three

competing treatments (i.e., stratified randomization). Participating men and women do not

know to which treatment they are assigned. They are instructed to take the assigned

medication when they experience joint pain and to record the time, in minutes, until the

pain subsides. The data (times to pain relief) are shown below and are organized by the

assigned treatment and sex of the participant.