Contraints on first and last p in POPAN models

Forum for discussion of general questions related to study design and/or analysis of existing data - software neutral.

Contraints on first and last p in POPAN models

Postby stshroye » Fri Nov 18, 2022 5:24 pm

I know that in fully time-dependent POPAN models, the first and last p need to be constrained in order for the superpopulation estimates to be valid. Schwarz and Arnason (1996) suggest fixing p(1) = p(k) = 1. However, is there any reason why they should not be fixed to something more informative? For example, what if there is evidence from CJS model {phi(.) p(t)} that the last p is much < 1?
stshroye
 
Posts: 27
Joined: Wed Sep 22, 2021 2:26 pm

Re: Contraints on first and last p in POPAN models

Postby jlaake » Wed Jan 24, 2024 7:42 pm

But your example depends on phi being constant and you don't know that. When you follow A&S suggestion, the last survival is simply the product of phi and p for that occasion. Likewise for occasion 1, it is p(1) and pent(1) that are confounded. A better solution is to use covariates or other information that lets you use other constraints like p(1)=p(2) and p(k-1)=p(k).
jlaake
 
Posts: 1417
Joined: Fri May 12, 2006 12:50 pm
Location: Escondido, CA


Return to analysis & design questions

Who is online

Users browsing this forum: No registered users and 6 guests