Figure 4.

Relationship between the a priori probability that an intervention will render a patient seizure free, α (horizontal axis), and the required seizure-free observation period before one the probability of future seizure freedom reaches 95%, according to Model #1 (see main text). The required waiting time is expressed in units equal to the mean pre-intervention interseizure interval. When the prior probability of seizure freedom is greater than 50%, 3 interseizure intervals is sufficient, and in fact for α = 80%, waiting approximately 1.5 intervals will theoretically suffice. By contrast, when the prior probability of success is less than 50%, a larger number of observation intervals is required, reaching roughly 6 intervals when α drops to 5%.