Technion, IEM faculty - Statistics Seminar
Speaker:  Danny Pfeffermann, Hebrew University,
Title:    Imputation and estimation under nonignorable nonresponse in
          household surveys with missing covariate information
Date:     27/11/2011
Time:     14:30
Place:    Bloomfield-527
Or read here:
In this paper we develop and apply new methods for handling not missing at
random (NMAR) nonresponse. We assume a model for the outcome variable
under complete response and a model for the response probability, which is
allowed to depend on the outcome and auxiliary variables. The two models
define the model holding for the outcomes observed for the responding
units, which can be tested. Our methods utilize information on the
population totals of some or all of the auxiliary variables in the two
models, but we do not require that the auxiliary variables are observed
for the nonresponding units. We develop an algorithm for estimating the
parameters governing the two models and show how to estimate the
distributions of the missing covariates and the outcomes. The latter
distributions are used for imputing the missing values of the
nonresponding units and for estimating population means and the variances
of the estimators. We consider several test statistics for testing the
combined model fitted to the observed data, which enables validating the
models used. The new developments are illustrated using a real data set
collected as part of the Household Expenditure Survey carried out by the
Israel Central Bureau of Statistics in 2005.
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