Ella Roelant

Multivariate generalized S-estimators

In this paper we introduce generalized S-estimators for the multivariate regression model. This class of estimators combines high robustness and high efficiency. They are defined by minimizing the determinant of a robust estimator of the scatter matrix of differences of residuals. In the special case of a multivariate location model, the generalized S-estimator has the important independence property, and can be used for high breakdown estimation in independent component analysis. Robustness properties of the estimators are investigated by deriving their breakdown point and the influence function. We also study the efficiency of the estimators, both asymptotically and at finite samples. To obtain inference for the regression parameters, we discuss the fast and robust bootstrap for multivariate generalized S-estimators. The method is illustrated on a real data example.

An L1-type estimator of multivariate location and shape

In this note we study a multivariate extension of the median obtained by considering the median as the L1 location estimator. Contrary to other multivariate extensions, this multivariate estimator yields simultaneously a location estimate and shape/scatter estimate. We investigate properties of the estimator such as the influence function and asymptotic variances and compare it with other estimators of location and shape.

Skin hydration in nursing home residents using disposable bed baths

The objective of this study was to evaluate a new way for applying bed baths and reducing the risk for dry skin by comparing the effect of two washing methods on skin hydration. A cluster randomized trial was conducted. Skin hydration was measured before and after implementation of disposable wash gloves, using a MoistureMeter SC at three skin sites. Total skin hydration did not differ between residents at the start of the study in both groups. After implementation, the post minus pre hydration scores were higher for the intervention group than the control group at all skin sites. However, the difference was only significant at cheek site. The use of disposable wash gloves does not increase the risk for dry skin in comparison with traditional washing methods. These results may encourage the introduction of disposable wash gloves as an innovation in daily skin care practice.