The data come from a Multicenter study comparing two oral treatments for toenail infection. Patients were evaluated for the degree of separation of the nail. Patients were randomized into two treatments and were followed over seven visits - four in the first year and yearly thereafter. The patients have not been treated prior to the first visit so this should be regarded as the baseline.
A data frame with 1908 observations on the following 5 variables.
ID of patient
0=none or mild seperation, 1=moderate or severe
the treatment A=0 or B=1
time of the visit (not exactly monthly intervals hence not round numbers)
the number of the visit
Lesaffre, E. and Spiessens, B. (2001). On the effect of the number of quadrature points in a logistic random-effects model: An example. Journal of the Royal Statistical Society, Series C, 50, 325-335.
G. Fitzmaurice, N. Laird and J. Ware (2004) Applied Longitudinal Analysis, Wiley