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Efficiency Comparisons in Multivariate Multiple Regression with Missing Outcomes

โœ Scribed by Andrea Rotnitzky; Christina A Holcroft; James M Robins


Publisher
Elsevier Science
Year
1997
Tongue
English
Weight
395 KB
Volume
61
Category
Article
ISSN
0047-259X

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โœฆ Synopsis


We consider a follow-up study in which an outcome variable is to be measured at fixed time points and covariate values are measured prior to start of follow-up. We assume that the conditional mean of the outcome given the covariates is a linear function of the covariates and is indexed by occasion-specific regression parameters. In this paper we study the asymptotic properties of several frequently used estimators of the regression parameters, namely the ordinary least squares (OLS), the generalized least squares (GLS), and the generalized estimating equation (GEE) estimators when the complete vector of outcomes is not always observed, the missing data patterns are monotone and the data are missing completely at random (MCAR) in the sense defined by Rubin [11]. We show that when the covariance of the outcome given the covariates is constant, as opposed to the nonmissing data case: (a) the GLS estimator is more efficient than the OLS estimator, (b) the GLS estimator is inefficient, and (c) the semiparametric efficient estimator in a model that imposes linear restrictions only on the conditional mean of the last occasion regression can be less efficient than the efficient estimator in a model that imposes article no. MV971660 102 0047-259Xร‚97 25.00


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