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IAI Actuarial Core Principles · Risk Modelling and Survival Analysis · Stochastic processes

A process is observed at all real times t ≥ 0, and at each time it takes one of the values in the finite set {Healthy, Sick, Dead}. How is this stochastic process classified by its time set and state space?

The process is continuous time with a discrete state space. Time can be any real number t ≥ 0, while the process only takes values in the finite set of three states, as in a standard health-sickness-death model.

  1. ADiscrete time, discrete state space
  2. BDiscrete time, continuous state space
  3. CContinuous time, continuous state space
  4. DContinuous time, discrete state spaceCorrect
  5. Continuous time, with a state space that is uncountably infinite

Explanation

The time index t takes any non-negative real value, so time is continuous. The states form a finite list, so the state space is discrete. Hence it is a continuous-time, discrete-state process, as in a multiple-state health model.

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