Frozen-age approximation in a multi-state model
= Frozen-age approximation in a multi-state model
A frozen-age approximation holds an age covariate constant at the start of each observation interval, allowing homogeneous <transition probabilities> to enter a <panel-observed multi-state likelihood>. It approximates a model with continuously changing age. Reciprocal rate calibration of mean waiting times is exact for a fixed-age <exponential distribution>, but not for a continuously ageing <Gompertz distribution>.