Likelihood Ratio Tests for Fixed Model Terms using Residual Maximum Likelihood

Likelihood ratio tests for fixed model terms are proposed for the analysis of linear mixed models when using residual maximum likelihood estimation. Bartlett-type adjustments, using an approximate decomposition of the data, are developed for the test statistics. A simulation study is used to compare properties of the test statistics proposed, with or without adjustment, with a Wald test. A proposed test statistic constructed by dropping fixed terms from the full fixed model is shown to give a better approximation to the asymptotic χ²-distribution than the Wald test for small data sets. Bartlett adjustment is shown to improve the χ²-approximation for the proposed tests substantially.     

Determination of a Tolerable Daily Intake of DDT for Consumers of DDT Contaminated Fish from the Lower Yakima River, Washington*

DDT, DDE, and DDD have been detected at elevated concentrations in sediments and fish of the Yakima River, its tributaries and drainages. An assessment was conducted to evaluate the public health significance of eating fish from the river. This was accomplished by establishing a daily intake level of DDT for the population of greatest concern, and comparing this level to a tolerable daily intake. The most sensitive and highly exposed group was determined to be breastfeeding infants. Infant daily intakes of DDT, based on estimated mother's DDT-breast milk levels, were compared to a recommended tolerable daily intake. Results indicate that mothers who frequently consume Yakima River bottom-feeding fish could have breast milk DDT concentrations sufficiently high to expose their infants to levels above the tolerable daily intake.     

How human resource outsourcing affects organizational learning in the knowledge economy

Adaptability and knowledge management, key elements of organizational learn-ing, are critical to organizational success as a result of a fundamental shift towards a knowledge economy. HR outsourcing and the growth in contingent work can result in a significant loss in learning capital through a breakdown in the psychological contract. We explore how to preserve HR's strategic role in facilitating organizational learning in the new outsourcing and offshoring con-text. The problem is compounded if outsourcing is introduced for cost control rather than strategic refocusing reasons. We suggest that managers can posi-tively influence the relationship between outsourcing and organizational learn-ing through internal marketing tactics and enriched psychological contracts. A previous version of this paper was presented at the Administrative Sciences Association of Canada (ASAC) Annual Meeting, Toronto, Canada, June 2005.     

Career Maturity in College Students With Learning Disabilities

This study compared levels of career maturity between college students with and without learning disabilities and investigated factors associated with career maturity. Few differences in career maturity were found. However, different predictors of career maturity for the two groups emerged. For students with learning disabilities, number of accommodations and quantity of work experience accounted for 22% of the variance in career maturity. For students without disabilities, academic achievement and type of work experience accounted for 21% of the variance in career maturity. Students with learning disabilities who received more instructional accommodations had lower levels of career maturity.     

Model and design correspondence in finite population sampling

A correspondence rule is suggested for the choice of a sampling design when prior knowledge concerning a finite population is available. Designs satisfying the correspondence rule are discussed in the case of random permutations models. A general optimality theorem is given for strategies under such models. Approximate correspondences satisfied by systematic sampling and πps sampling are also indicated.     

Animal Magic: Nigel Nicholson and Evolutionary Psychology

Nicholson, N., Managing the Human Animal: Why People Behave the Way They Do in Corporate Settings