We discuss a stochastic model appropriate for binary data in clinical
studies where assessments are made at various nominal times during a t
reatment phase. The model is then applied to data on headache relief,
nausea and photophobia/phonophobia in a migraine study. The transition
rates and probabilities during the initial 240 minutes after treatmen
t administration are derived using the method of maximum likelihood. T
he results are then compared with analysis at each nominal time point.
Stochastic modelling is considered more appropriate for the analysis
of repeated binary assessments than analysis at each nominal time sinc
e each patient's assessments are modelled simultaneously.