Dear all,

I've got a query about the Cox hazard models used by Gartner (APSR, 102:1 (2008), pp. 95-106).  He runs a panel experiment in which monthly casualty rates during a conflict are manipulated, and the hazard models gauge the impact of these manipulations on the duration of public support for military action.  Gartner's panel has ten waves, i.e. ten opportunities to choose between leaving the troops in or bringing them home.  In planning a similar design, I was wondering about the amount of flexibility available concerning this number of waves.  I guess that, under the model's assumptions, duration is a continuous variable, but obviously it is necessarily discrete in this kind of design.  So can anyone suggest a rough rule on how many time periods would be needed to estimate such hazard models accurately?

Many thanks,

Rob Johns.

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