16 Discrete Event Simulation for Health Technology Assessment
would require many states—numbering into the thousands—to represent
unique combinations of these factors and maintaining that heterogeneity
throughout the model. This is tantamount to creating a separate version of
the model for each distinct set of characteristics or undertaking separate
analyses for each prole. Even so, there remains the challenge of putting all
those results back together to represent the costs and effects in the aggre-
gated population, or subgroups. In a DES, individuals are assigned their
own unique values for the set of characteristics, including memory of all
that has happened. These values—updated as appropriate throughout the
simulation—control what happens ...