IN BOTH XOVER1 DATA A AND XOVER2 DATA A, THE VARIABLES WERE CODED AS FOLLOWS. ID = CLUSTER VARIABLE CLASS = 1, NEEDED TO RUN GEE2 Y = 1 IF AFFECTED AND 0, O.W. X1 = 1 (INTERCEPT) X2 = 1 IF TX B AND 0 IF TX A X3 = 1 IF PERIOD 2 AND 0 IF PERIOD 1 X4 = X2*X3 X5 = 1 IF BA AND 0 IF AB (NEEDED FOR REGRESSION MODEL ON OR) REFERENCES : XOVER1 DATA IS FROM JONES AND KENWARD(1989) CHAPMAN AND HALL, P.9