Sometimes it is of interest to assume that the survival function
follows a parametric model, i.e. it is of the form S(x, θ), where θ
is an unknown parameter. There are several reasons to make this
assumption:
1. Data supports this assumption. Actuaries realized that the
models observed in real life follow this assumption.
2. Computations are simpler using a parametric model.
3. There are valid scientific reasons to justify the use of a
particular parametric model