Volume 48 | Number 5 | October 2013

Abstract List

Chuan‐Fen Liu M.P.H., Ph.D., James F. Burgess Ph.D., Willard G. Manning, Matthew L. Maciejewski Ph.D.


To illustrate how the analysis of bimodal U‐shaped distributed utilization can be modeled with beta‐binomial regression, which is rarely used in health services research.

Data Sources/Study Setting

Veterans Affairs () administrative data and Medicare claims in 2001–2004 for 11,123 Medicare‐eligible primary care users in 2000.

Study Design

We compared means and distributions of reliance (the proportion of all /Medicare primary care visits occurring in ) predicted from beta‐binomial, binomial, and ordinary least‐squares () models.

Principal Findings

Beta‐binomial model fits the bimodal distribution of reliance better than binomial and models due to the nondependence on normality and the greater flexibility in shape parameters.


Increased awareness of beta‐binomial regression may help analysts apply appropriate methods to outcomes with bimodal or U‐shaped distributions.