Fitting E(max) models to clinical trial dose-response data

We consider fitting Emax models to the primary endpoint for a parallel group dose–response clinical trial. Such models can be difficult to fit using Maximum Likelihood if the data give little information about the maximum possible response. Consequently, we consider alternative models that can be derived as limiting cases, which can usually be fitted. Furthermore we propose two model selection procedures for choosing between the different models. These model selection procedures are compared with two model selection procedures which have previously been used. In a simulation study we find that the model selection procedure that performs best depends on the underlying true situation. One of the new model selection procedures gives what may be regarded as the most robust of the procedures.     

Improving bank operations: A case study at BancOhio/Ohio National Bank

The paper describes the procedures employed at Ohio National Bank to improve operations of the check handling and clearing system. It illustrates the approaches utilized to (1) schedule messenger vehicles, (2) determine worker shift schedules, (3) forecast daily work loads and (4) develop work priorities. These four tasks improved productivity and reduced float at the bank. Also discussed is the data required to utilize the formal planning procedures illustrated. The paper indicates the financial impact of this work and future efforts in a dynamic banking environment.     

Visualising interaction effects

In drug discovery, statisticians often work with biologists and chemists to uncover relationships between the various chemical properties and the biological effects of compounds. The aim is to "design" drugs that have exactly the desired pharmaceutical effects. Phil Woodward and Mark Whitlock of Pfizer Global R&D show how a graph can uncover deeply hidden relationships and guide chemists in their efforts to find the next blockbuster drug.     

Structure,agency, and the Nicaraguan Revolution

Theory and Society -     

Violence at work: An issue for the 1990s

Violence and conflict appear to be increasingly common aspects of everyday life, to the point where people take them into consideration when planning their activities and feel anxious about their possible occurrence. It is not only actual violence which offers a contemporary source of stress but also the threat of violence, although subjective estimates of risk are not always accurate. For example, it would appear that while the elderly feel the most threatened, the greatest risk is to those in their late teens and early twenties. This discrepancy between objective and subjective risk is understandable in terms of the different factors which have been shown to drive the subjective assessment of risk: availability of information, controllability and magnitude of outcome. Often it is the media which provides us with the information that we have on violence, and it is that presentation of information which helps shape our assessment of risk. For example, attacks by young persons on the elderly may be more dramatic and newsworthy than, albeit more frequent, attacks on other young persons. Thus they are reported to a greater extent and a distorted impression of risk begins to develop, which may be reinforced by realistic feelings of potential helplessness by the elderly in the face of any such attack, and fear of the magnitude of the consequences of violence. Whatever the real basis for a fear of violence, the available statistics in most European and North American countries suggests that, even taking into account the effects of reporting bias, acts of violence are increasing.     

Investigating the link between the Pill and cancer

Does the contraceptive pill increase the risk of cancer? The question has been asked ever since the pill was introduced, and is one that must worry almost every woman in the country. Small wonder that when the results of a long-term study, which began 40 years ago, came out in the autumn it made front-page headlines. As Phil Hannaford explains, answering the question was not straightforward.     

ESTIMATING EQUATIONS AND NON-LINEAR FUNCTIONAL RELATIONSHIPS

A nonlinear functional relationship is defined as an R-dimensional manifold in P-dimensional space. The formulation of the model may be explicitly in terms of R-dimensional vectors of incidental parameters or implicitly by a (P-R)-dimensional vector function of constraints. The objective is to estimate and make inference about a K-vector of parameters θ which defines the manifold. Each observed P-vector has its expectation lying on the manifold, and the error vector has a variance matrix defined in terms of a further vector of parameters The theory of estimating equations in the presence of incidental parameters is extended and applied to the explicit formulation, to give equations suitable for estimating θ given knowledge of only the first two moments. The method has a geometrical interpretation. Estimating equations for are chosen to be those which would be optimal if the normality assumption were true. First order corrections to the biases of these estimates are included. An example where the manifold is a circle centred on the origin is used to illustrate the theory. Further examples incorporate more general features, including the estimation of two variance parameters and estimation in higher dimensions.     

Job Insecurity and Employee Commitment: Managers' Reactions to the Threat and Outcomes of Redundancy Selection1

Increases in managerial redundancies have followed in the wake of recession and fiercer competition. Although popular accounts have warned of a growing disaffection among managers, few studies have examined the effects of abandoning their traditional job security. This article examines changes in the work attachments of long-service managers under the threat of redundancy. Over a 12-month period, interviews were conducted with 42 middle managers who, at the beginning of the research, had been warned of possible redundancy. Initially, most of the managers experienced significant threats to their established views about themselves and their employers. The development of these early perceptions into altered work attachments depended largely on outcomes of the redundancy process. For reprieved managers organizational commitment was quickly re-established. In contrast, those demoted to engineering roles or re-employed by other companies became less trusting and developed new explanations of their past employment experiences. These findings illustrate the tension between the need of managers to be assured of their place within the organizational structure and recent threats to their traditional careers and employment security. Also we may expect difficulties in the development of organizational commitment to emerge as the personal risks to managers increase.     

Religiosity as a Potential Moderator of the Effects of R-rated Movies on Delinquency

Previous research suggests viewing R-rated movies is associated with delinquency (Tanski et al. 2010 Tanski , Susanne E. , Sonya Dal Cin , Mike Stoolmiller , and James D. Sargent . 2010. “Parental R-Rated Movie Restriction and Early-Onset Alcohol Use.” Journal of Studies on Alcohol and Drugs 71(3):452–460.[PubMed], [Web of Science ®] , [Google Scholar]; Titus-Ernstoff et al. 2008 Titus-Ernstoff , L. , M. A. Dalton , A. M. Adachi-Mejia , M. R. Longacre , and M. L. Beach . 2008 . “Longitudinal Study of Viewing Smoking in Movies and Initiation of Smoking by Children.” Pediatrics 121 : 15 – 21 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), while religiosity leads to decreases in substance use (Jang and Johnson 2001 Jang , Sung Joon and Byron R. Johnson . 2001 . “Neighborhood Disorder, Individual Religiosity, and Adolescent Use of Illicit Drugs: A Test of Multilevel Hypotheses.” Criminology 39 ( 1 ): 109 – 144 .[Crossref], [Web of Science ®] , [Google Scholar]; Kovacs, Piko, and Fitzpatrick 2011 Jang , Sung Joon and Byron R. Johnson . 2011 . “The Effects of Childhood Exposure to Drug Users and Religion on Drug Use in Adolescence and Young Adulthood.” Youth and Society 43 : 1220 – 1245 .[Crossref], [Web of Science ®] , [Google Scholar]; Miller 1998 Miller , W. 1998 . “Researching the Spiritual Dimensions of Alcohol and Other Drug Problems.” Addiction 93 : 979 – 990 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Regnerus 2003 Regnerus , Mark D. 2003 . “Moral Communities and Adolescent Delinquency: Religious Contexts and Community Social Control.” Sociological Quarterly 44 : 523 – 554 .[Crossref], [Web of Science ®] , [Google Scholar]). However, the influences of religiosity and viewing R-rated movies have not been examined in conjunction. This article tests whether religiosity moderates the effects of R-rated movies on delinquency, results suggesting that rather than religiosity moderating the effects of R-rated movies on delinquency, viewing R-rated movies actually tempers the pro-social effects of religiosity. This finding only held true for certain types of substance abuse, and not activity-based forms of delinquency such as fighting. The results are discussed in light of their implications for the current study of the effects of religiosity on delinquency, and suggestions are made for future research on the relationship between viewing R-rated movies and delinquency.