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Seminário
Conjunto UFSCar/ICMC ? 11/04/2014 - 14h00
LOCAL:
Auditório
Luiz Antonio Favaro (1º andar do Bloco 4 no ICMC-USP) TITLE: Imputation and
Estimation under Nonignorable Nonresponse in Household Surveys with Missing
Covariate Information ABSTRACT:
In this article 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. |