Doris Hertsgaard

Distribution of asymmetric trimmed means

The empirical distribution of asymmetrically trimmed means is investigated by means of Monte Carlo studies. It is shown that if the trimming is done as suggested in the paper, the resulting standardized statistic has an approximate Students t-distribution. The power of these trimmed means is demonstrated by means of a Monte Carlo study comparing a statistic which is a function of the trimmed means to the usual two-sample t-test.

A collinearity diagnostic for nonlinear regression

A possible way of diagnosing collinearity among independent random variables in nonlinear regression models is examined. This diagnostic procedure is used in a simulation study involving three different nonlinear models and the results are discussed.

A Developmental Visual Assessment for Children with Multiple Handicaps.

This paper describes the development of a visual-motor evaluation instrument, reports an interrater reliability study, and illustrates the instruments use in a preschool handicapped program. During Phase 1 an extensive literature search led to a compiled set of developmental norm data for reflexive and voluntary visual-motor development. Phase 2 included clinical use and revision of the resultant Erhardt Developmental Vision Assessment (EDVA). Phase 3 involved testing the EDVA for interrater reliability, which resulted in highly significant interrater agreement with the test author. A sample application is illustrated by segments of an EDVA used to integrate visual-motor components into an Individualized Program Plan (IPP).