A likelihood ratio test for the equality of proportions of two normal populations

In sampling inspection by variables, an item is considered defective if its quality characteristic Y falls below some specification limit L₀. We consider switching to a new supplier if we can be sure that the proportion of defective items for the new supplier is smaller than the proportion defective for the present supplier.

Assume that Y has a normal distribution. A test for comparing these proportions is developed. A simulation study of the performance of the test is presented.     

New representations of the noncentral chi-square density and cumulative

Representations of noncentral chi-square cumulative distribution function and probability density function are reviewed and new repre¬sentations are given. One representation of the cdf in terms of an integral is easily computed on any machine which has an accurate algorithm for computing the normal cdf.     

Dependence in the 2001 one-number census project

Summary.  The one-number census approach was developed by the Office for National Statistics to adjust the counts from the 2001 census of England and Wales for underenumeration. The method is underpinned by an assumption of independence between the count of the population that was given by the 2001 census and the count that was given by the Census Coverage Survey. Some dependence was, however, detected, and the paper describes the strategy that was used to measure dependence and to adjust the 2001 census population estimates.     

Sample size calculations for clinical studies allowing for uncertainty about the variance

One of the most important steps in the design of a pharmaceutical clinical trial is the estimation of the sample size. For a superiority trial the sample size formula (to achieve a stated power) would be based on a given clinically meaningful difference and a value for the population variance. The formula is typically used as though this population variance is known whereas in reality it is unknown and is replaced by an estimate with its associated uncertainty. The variance estimate would be derived from an earlier similarly designed study (or an overall estimate from several previous studies) and its precision would depend on its degrees of freedom. This paper provides a solution for the calculation of sample sizes that allows for the imprecision in the estimate of the sample variance and shows how traditional formulae give sample sizes that are too small since they do not allow for this uncertainty with the deficiency being more acute with fewer degrees of freedom. It is recommended that the methodology described in this paper should be used when the sample variance has less than 200 degrees of freedom.     

Chemical Scoring by a Rapid Screening of Hazard (RASH) Method

A rapid screening of hazard method (RASH) is presented for deriving relative potency estimates for hazardous substances. The method utilizes data from any available toxicological database such as the Registry of Toxic Effects of Chemical Substances (RTECS) or EPA's GENE-TOX database on genetic activity profiles. The method has been applied to derive relative potency values and permissible environmental concentrations for 278 chemicals. The derived values have been compared with recommendations of expert committees where possible, and substantial agreement is found.     

Time and time again: Implications of time perception theory

This article explores the integration of time perception theory from various root disciplines related to family resource management. It includes anthropological models of time perception and sociological and psychological concepts related to time measure and usage. Examples of issues appropriate to the exploration of time use in the home and instrumentation that may assist in its understanding and measurement are included.This research was supported in part by Lincoln University Cooperative Research.Alma J. Owen is Associate Professor and Small Farm Family Program Leader for Lincoln University Cooperative Extension, 900 Moreau Drive, Jefferson City, MO 65101. Her research interests include measuring household production, at-home income generation, and rural families. She received her Ph.D. in Family and Consumer Economics from the University of Missouri-Columbia.     

Thirteen theorems in search of the truth

We review recent work on the accuracy of group judgmental processes as a function of (a) the competences (judgmental accuracies) of individual group members, (b) the group decision procedure, and (c) group size. This work on individual competence and group accuracy represents an important contribution to democratic theory and a useful complement to the usual emphasis in the social choice literature on individual preference and preference aggregation mechanisms. The work reported on is rooted in a tradition which goes back to scholars such as Condorcet, Poisson, and Bayes.     

A game theoretic approach to measuring degree of centrality in social networks

We present a new measure of degree of centrality in a social network which is based on a natural extension of the Banzhaf (1965) index of power in an N-person game.