ON THE DERIVATION AND COMPUTATION OF THE CORNISH-FISHER EXPANSION

The paper gives a simple derivation based on elementary statistics for the Cornish—Fisher expansion. The method simplifies greatly the algebra in working out the polynomials involved both in the normalization and in the inverse expansions. The derivation also leads to recursive formulae which yield powerful algorithms for numerical computation of the expansion.     

False parsimony and its detection with GLMs

A search for a good parsimonious model is often required in data analysis. However, unfortunately we may end up with a falsely parsimonious model. Misspecification of the variance structure causes a loss of efficiency in regression estimation and this can lead to large standard-error estimates, producing possibly false parsimony. With generalized linear models (GLMs) we can keep the link function fixed while changing the variance function, thus allowing us to recognize false parsimony caused by such increased standard errors. With data transformation, any change of transformation automatically changes the scale for additivity, making false parsimony hard to recognize.     

Statistical morphology

This paper first introduces a parametric model for the generation of stationary random correlated binary sequences. The parameters of the model include the probability that a pixel is a binary one pixel and the length of the structuring element which dilates the initially spatially uncorrelated sequence. The spatial statistics of such eroded, dilated, opened and closed correlated binary sequences are derived in terms of the spatial statistics of the input binary sequence. Understanding of such one-dimensional processing is a precondition for understanding what happens in the more interesting two- dimensional case.     

Problem behaviors,substance abuse and sexual abuse in psychiatrically hospitalized adolescents with bulimia nervosa

Twenty-eight adolescent bulimics were compared to 201 psychiatrically hospitalized non-eating disordered patients. Non-eating disordered patients were found to be reliably more aggressive, delinquent, and under-controlled than patients with bulimia nervosa. Sexual abuse was found to be less prevalent among bulimic adolescents than comparison adolescents. No significant between group differences were achieved on any measure of alcohol/drug abuse. The behavioral profiles of substance abusing bulimics were highly similar to those of non-eating disordered patients. Three months follow-up of bulimic patients found that they were less depressed, had less somatization, and were less overcontrolled; however, they showed no reliable improvements in eating attitudes/behaviours or drug/alcohol use.