Spline Pattern-Mixture Models for Missing Data
Volume 19, Issue 1 (2021), pp. 75–95
Pub. online: 10 February 2021
Type: Statistical Data Science
Received
1 November 2020
1 November 2020
Accepted
1 January 2021
1 January 2021
Published
10 February 2021
10 February 2021
Abstract
We consider a continuous outcome subject to nonresponse and a fully observed covariate. We propose a spline proxy pattern-mixture model (S-PPMA), an extension of the proxy pattern-mixture model (PPMA) (Andridge and Little, 2011), to estimate the mean of the outcome under varying assumptions about nonresponse. S-PPMA improves the robustness of PPMA, which assumes bivariate normality between the outcome and the covariate, by modeling the relationship via a spline. Simulations indicate that S-PPMA outperforms PPMA when the data deviate from normality and are missing not at random, with minor losses of efficiency when the data are normal.
Supplementary material
Supplementary MaterialPlease refer to the Supplementary Material document for: 1. A detailed description of the Gibbs sampling algorithm for the penalized spline prediction. 2. Results from all six simulation scenarios, including estimates from
n = 100
and
n = 400
and where
λ A = λ T
and
λ A ≠ λ T
. 3. R code and workspace for the simulations.