Health-related variables and academic performance among first-year college students: implications for sleep and other behaviors

The authors analyzed the effect of several health behaviors and health-related variables on grade point averages of a random sample of 200 students living in on-campus residence halls at a large private university. The set of variables included exercise, eating, and sleep habits; mood states; perceived stress; time management; social support; spiritual or religious habits; number of hours worked per week; gender; and age. Of all the variables considered, sleep habits, particularly wake-up times, accounted for the largest amount of variance in grade point averages. Later wake-up times were associated with lower average grades. Variables associated with the 1st-year students' higher grade point averages were strength training and study of spiritually oriented material. The number of paid or volunteer hours worked per week was associated with lower average grades.     

A note on the linear discriminant function when group means are equal

The performance of the sample linear discriminant function with known, proportional, covariance matrices and equal but unknown mean vectors is considered. Unconditional misclassification rates are obtained from the Student-t distribution. These results can be used as an aid in verifying simulation programs incorporating the linear discriminant function when Gaussian densities with unequal covariance matrices are used.     

The magnitude of the difference of crude and adjusted log odds ratios

Crude and adjusted odds ratios, calculated from a collapsed 2×2 table or a stratified 2×2×K table, can be very similar or quite different when significant associations are found between each dichotomous variable and the K-level stratifying variable. It is demonstrated here that the magnitude of the difference between the logs of the two estimators can be approximated by 4 times the covariance between log linear interactions describing the associations of each of the binary variables with the stratifying variable. Two data examples illustrate the usefulness of the variability and covariability of the interactions in providing a statistical accounting for the magnitude of the difference between the logs of the crude and adjusted odds ratios. Other interpretations and applications of the variances and covariances of the log linear interactions are discussed.     

A universal meta bargaining implementation of the Nash solution

This paper follows van Damme (1986) in presenting a meta bargaining approach that justifies the Nash bargaining solution. But in contrast to van Damme's procedure our meta bargaining game is universal in the sense that all bargaining solutions are allowed as strategic choices in the meta bargaining game. Also our result holds true for any number n of players. Received: 31 July 2000/Accepted: 19 March 2001     

An inspection game of internal audit and the influence of whistle-blowing

In this paper we analyse how whistle-blowing affects fraudulent behaviour of managers while the company instigates imperfect internal audit to detect the fraud. To do so, we employ in a first step a non-cooperative inspection game to analyse fraudulent behaviour of a manager controlled by an internal auditor. In a second step we introduce exogenous whistle-blowing of a manager’s employee to aid the auditor to reveal the fraud. In a third step, the two-person inspection game is extended to a three-person approach with endogenous whistle-blowing. Our novel results are that the intensity of internal audit is always lower with whistle-blowing than without and that whistle-blowing renders the manager to act less fraudulently than compared to the basic inspection game if and only if she is unaware of the whistle-blower’s expected pay-off and the efficacy of internal audit is sufficiently low.     

The effects of urbanization on body size of larval stream salamanders

Animal body sizes in urban areas often differ from nearby rural areas, which may impact population fitness and dynamics. We examined the effects of urbanization on larval body sizes of two species of salamanders, the two-lined salamander (Eurycea cirrigera) and the northern dusky salamander (Desmognathus fuscus). Specifically, we utilized a before-after control-impact (BACI) study design which allowed for the assessment of differences in larval body size between multiple control and impacted sites over a 5 year period. We found a decrease in larval body size in both species at the impacted sites compared to control sites in the first year after urbanization, followed by generally larger body sizes in urban sites compared to control sites in years 3–5, and significantly so in year 4. Using generalized linear models, we found support that larger body sizes post impact in urbanized streams may be due to warmer stream water temperature and decreased abundance of larvae. Both E. cirrigera and D. fuscus are well known for their ability to persist in urbanized streams; our data suggest that despite overall lower abundances in urban streams, persistence may be due to increases in larval body size and, potentially, post-metamorphic benefits.