Bootstrap Estimation of Benchmark Doses and Confidence Limits with Clustered Quantal Data

The benchmark dose (BMD) is an exposure level that would induce a small risk increase (BMR level) above the background. The BMD approach to deriving a reference dose for risk assessment of noncancer effects is advantageous in that the estimate of BMD is not restricted to experimental doses and utilizes most available dose-response information. To quantify statistical uncertainty of a BMD estimate, we often calculate and report its lower confidence limit (i.e., BMDL), and may even consider it as a more conservative alternative to BMD itself. Computation of BMDL may involve normal confidence limits to BMD in conjunction with the delta method. Therefore, factors, such as small sample size and nonlinearity in model parameters, can affect the performance of the delta method BMDL, and alternative methods are useful. In this article, we propose a bootstrap method to estimate BMDL utilizing a scheme that consists of a resampling of residuals after model fitting and a one-step formula for parameter estimation. We illustrate the method with clustered binary data from developmental toxicity experiments. Our analysis shows that with moderately elevated dose-response data, the distribution of BMD estimator tends to be left-skewed and bootstrap BMDL s are smaller than the delta method BMDL s on average, hence quantifying risk more conservatively. Statistically, the bootstrap BMDL quantifies the uncertainty of the true BMD more honestly than the delta method BMDL as its coverage probability is closer to the nominal level than that of delta method BMDL. We find that BMD and BMDL estimates are generally insensitive to model choices provided that the models fit the data comparably well near the region of BMD. Our analysis also suggests that, in the presence of a significant and moderately strong dose-response relationship, the developmental toxicity experiments under the standard protocol support dose-response assessment at 5% BMR for BMD and 95% confidence level for BMDL.     

Formalization of grievance procedures: A multi-firm and industry study

This study examines how two aspects of formalization of grievance procedures affect grievance procedure effectiveness: written versus oral presentation of grievance and the level of union and management authorized to resolve grievances at the first step. Several demographic variables were controlled for: size of bargaining unit, percentage of organization represented, number of grievances filed, and industry. A sample of 46 firms, representing a broad cross-section of unionized companies in the private sector, was obtained with the help of the American Arbitration Association. Results indicate that more formal grievance procedures (e.g., written presentation) are positively related to resolution rates at the first step. The number of grievances field and the size of the bargaining unit were positively related to total resolution rates prior to arbitration. We thank the American Arbitration Association for making this study possible.     

Portmanteau test for conditional heteroscedasticity, using ranks of squared residuals

Squared residual autocorrelations have been found useful in detecting departures from linearity in time series models. This is especially the case with data exhibiting heterogeneity in variances. A rank test is proposed which is much more robust than its parametric counterpart.     

Effects of Category Order on Answers in Mail and Telephone Surveys1

Abstract Past research suggests that mail surveys encourage a primacy effect, which is a tendency to choose the first answers from a list, whereas telephone surveys encourage a recency effect, a tendency to choose the last answers from a list. This paper summarizes results from 82 new experiments conducted in 12 separate surveys in seven states. Only four of 33 mail survey comparisons exhibited significant primacy effects, while five of 26 experiments in telephone surveys exhibited recency effects. In addition, only three of 23 cross-method comparisons produced a significant primacy/recency effect in the expected manner. The conclusion is that the prevalence of primacy and recency effects has been over-estimated by past research and a new theoretical approach that takes into account multiple causation is needed for examining these effects.     

Beyond recruitment: Predictors of differential participation in a national antihunger organization

Surprisingly little research has sought to explain differential participation after recruitment into social movement organizations (SMOs). This study examines the influence of several sets of predictors on participation by members of a national organization in the antihunger movement. The findings highlight the importance of incentive, ideological, and microstructural factors for differential participation and suggest that favorable perceptions of SMOs also promote participation. Final remarks address the implications of the findings for the social movement and voluntary organization literatures.     

log-logistic survival estimation based on failure-censored data

Approximations of the Bayesian estimators of the survival function based on the censored data of the log-logistic distribution are obtained under squared-error and log-odds squared-error loss functions. A numerical example is presented. Through a Monte Carlo simulation study, the behavior of the approximations found by Tierney & Kadane and Lindley are compared with a method suggested by Weiss & Howlader.     

Socialization of emotion: Pathway to preschoolers' emotional and social competence

Aspects of 47 preschoolers'emotional competence—their patterns of emotional expressiveness and reactions to others' emotion displays—were observed in two settings, with mother and with peers, and their general social competence was rated by their preschool teachers. Intrapersonal and interpersonal (i.e., socialization correlates of children's emotional competence were identified, and a causal model incorporating direct and indirect influences on social competence was evaluated. Maternal patterns of expressiveness, reactions to children's emotion displays, and self-reported affective environment were associated with children's emotional competence in the preschool. Children's emotional competence with mother predicted their emotional competence in the preschool somewhat less strongly, suggesting that emotional competence may differ according to the interpersonal relationship studied. Taken as a whole, findings reassert the importance of the domain of emotional expression to the development of social competence.Reprint requests can be sent to the author, Department of Psychology, George Mason University, 4400 University Drive, Fairfax, VA 22030. Grateful acknowledgment goes to the mothers and children who so clearly expressed and reacted to emotions; thanks also are due to Christine Alban, Joanne Ayyash, Michael Casey, Elizabeth Couchoud, Huynh Dung, Merlina Hemingway, Soueang Lay, Vanna Nguyen, Emilianne Slayden and Kimberly Sproul, as well as the director and teachers of the Project for the Study of Young Children. An earlier version of this material was presented at the 1991 Biennial Meetings of the Society for Research in Child Development, Seattle, WA. University support from Grants #2-10150, 2-10176 and 2-10073 also made the research possible.