TY  - JOUR
PY  - 2008//
TI  - Assessing influence for pharmaceutical data in zero‐inflated generalized Poisson mixed models
JO  - Statistics in Medicine
A1  - Xie, Feng‐Chang
A1  - Wei, Bo‐Cheng
A1  - Lin, Jin‐Guan
SP  - 3656
EP  - 3673
VL  - 27
IS  - 18
N2  - For clustered count data with excess zeros where the observations are either over-dispersed or under-dispersed, the zero-inflated generalized Poisson mixed (ZIGPM) regression model may be appropriate, in which the baseline discrete distribution is a generalized Poisson distribution, which is a natural extension of standard Poisson distribution. Motivated by one data set drawn from a pharmaceutical study, influence diagnostics for ZIGPM models based on case-deletion and local influence analysis are developed in this work. The one-step approximations of the estimates under case-deletion model and some case-deletion measures are given. Meanwhile, local influence measures are obtained under various perturbations of the observed data or model assumptions. Results from a pharmaceutical study illustrate the usefulness of the diagnostic statistics. Copyright © 2008 John Wiley & Sons, Ltd.<p /> 
LA  - 
SN  - 0277-6715
UR  - http://dx.doi.org/10.1002/sim.3233
ID  - ref1
ER  -