# SCH

## Seminar

### Estimating a response parameter in missing data models with high-dimensional covariates

van der Vaart, AW (Amsterdam)
Thursday 10 January 2008, 09:00-10:00

Seminar Room 1, Newton Institute

#### Abstract

We discuss a new method of estimation of parameters in semiparametric and nonparametric models. The method is based on estimating equations that are $U$-statistics in the observations. The $U$-statistics are based on higher order influence functions that extend ordinary linear influence functions of the parameter of interest, and represent higher derivatives of this parameter. For parameters for which the matching cannot be perfect the method leads to a bias-variance trade-off, and results in estimators that converge at a slower than root-n-rate. In a number of examples the resulting rate can be shown to be optimal. We are particularly interested in estimating parameters in models with a nuisance parameter of high dimension or low regularity, where the parameter of interest cannot be estimated at root-n-rate.

#### Video

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