There has been considerable attention on estimation of conditional variance function in the literature. We propose here a nonparametric model for conditional covariance matrix. A kernel estimator is developed accordingly, its asymptotic bias and variance are derived, and its asymptotic normality is established. A real data example is used to illustrate the proposed estimation procedure.

Directional effects introduce a variability in reflectance and vegetation index determination, especially when large field-of-view sensors are used (e.g., Moderate Resolution Imaging Spectroradiometer - MODIS). In this study, we evaluated directional effects on MODIS reflectance and four vegetation indices (Normalized Difference Vegetation Index - NDVI; Enhanced Vegetation Index - EVI; Normaliz...

We suggest a method for using nonparametric information to modify a parametric model at a low-order level, retaining information in the model only to enhance the nonparametric approach at relatively high orders. Our technique represents an alternative to methods that rst t a parametric model and then adjust it. In particular, relative to a \nonparametric estimator with a parametric start," our ...

OBJECTIVES This article compares suicide in the immigrant and Canadian-born populations. DATA SOURCES The suicide data are from the Canadian Vital Statistics Data Base and the World Health Statistics Annual of the World Health Organization. The socio-demographic information used to determine denominators for suicide rates in Canada comes from the Census of Population. ANALYTICAL TECHNIQUES ...

Partial linear model is very flexible when the relation between the covariates and responses, either parametric and nonparametric. However, estimation of the regression coefficients is challenging since one must also estimate the nonparametric component simultaneously. As a remedy, the differencing approach, to eliminate the nonparametric component and estimate the regression coefficients, can ...

PURPOSE Our study documents how the divorce rate among persons aged 50 and older has changed between 1990 and 2010 and identifies the sociodemographic correlates of divorce among today's middle-aged and older adults. DESIGN AND METHOD We used data from the 1990 U.S. Vital Statistics Report and the 2010 American Community Survey (ACS) to examine the change in the divorce rate over time. ACS da...