Data from randomized crossover study comparing two analgesic drugs (A and B)
and placebo for relief of tension headaches.


Reference: Laird, N.M., Skinner, J. and Kenward, M. (1992). An analysis of 
two-period crossover designs with carry-over effects. Statistics in Medicine,  
11, 1967-1979).


Description:

The study was designed to compare two active drugs and placebo for 
relief of tension headache. The two analgesic drugs were identical in their 
active ingredients except that one contained caffeine. The primary comparison 
of interest was between the two active drugs; the placebo was included for
regulatory purposes. 
Note that there were three treatments, but only two periods, i.e.,
each subject received only two of the three treatments in a random
order.  With three treatments and two periods, there are six
possible treatment sequences, AB, BA, AP, PA, BP, PB, where A, B
and P denote the two active drugs and placebo.  
In this study the AB and BA sequences were assigned three times as 
many subjects as the remaining four because of the interest in the A 
versus B comparison. 
Note: Two headaches treated within each period and response is the
average pain relief for both headaches.


Variable List: 

ID, Center, Treatment Sequence (1-6), Period (0,1), 
Treatment (P,A,B), Response (Pain relief).