Practical guide to sample size calculations: an introduction

A sample size justification is a vital step when designing any trial. However, estimating the number of participants required to give a meaningful result is not always straightforward. A number of components are required to facilitate a suitable sample size calculation. In this paper, the general steps are summarised for conducting sample size calculations with practical advice and guidance on how to utilise the app SampSize. Copyright © 2015 John Wiley & Sons, Ltd.     

Role versatility among men who have sex with men in urban Peru

Role versatility refers to the practice in which individual men who have sex with men (MSM) play both insertive and receptive sexual roles over time. Versatility has been thought to be relatively uncommon among Latin American MSM but possibly rising. Versatility has also been shown to be a potentially large population-level risk factor for HIV infection. In this study we examine the correlates of versatile behavior and identity among 2,655 MSM in six Peruvian cities. Versatile behavior with recent male partners was found in 9% of men and versatile ("moderno") identity was reported by 16%. Significant predictors included high education, white-collar occupation, sex work, and residence in Lima. Age was not significant in any analysis. Since sex work is negatively correlated with other predictors, versatile men appear to comprise two distinct sub-populations. Insertive-only men appear to play a strong role in bridging the HIV epidemic between MSM and women.     

When do simpler sexual behavior data collection techniques suffice? An analysis of consequent uncertainty in HIV acquisition risk estimates

The "gold standard" for evaluating human immunodeficiency virus (HIV) prevention programs is a partner-by-partner sexual behavior assessment that elicits information about each sex partner and the activities engaged in with that partner. When collection of detailed partner-by-partner data is not feasible, aggregate data (e.g., total numbers of partners and acts of various types) must suffice. Lack of specificity in the primary data often translates into uncertainty in modeled outcomes, such as participants' risk of HIV acquisition. To our knowledge, no previous study has attempted to quantify this uncertainty. The results of the present analysis of the risk of HIV acquisition by men vacationing in Key West indicate that the use of aggregate rather than partner-by-partner data introduced relatively little uncertainty into the HIV risk estimates. Collection of aggregate data is a viable alternative to detailed partner-by-partner data, at least in some circumstances.     

Toward a pragmatic program for critical urban ecology

Our essay responds to the critique of Dooling et al. (Urban Ecosystems in press, 2007) of our previously published article “Goal attainment in urban ecology research: a bibliometric review 1975-2004 (Young and Wolf, Urban Ecosystems, 9:179–193, 2006). We identify our critics’ concerns as rooted in a project of deconstruction of scientific inquiry and a redefinition of the boundaries separating academic disciplines from each other and science from society. While we identify important differences with our critics, we largely support this critical project, as evidenced by our previously published empirical research. In exploring the relationship between critical and positivist approaches to urban ecology research and how we might work toward an integration of nature and society in thought and action, we defend pragmatic approaches to empirical research as well as disciplinary projects as legitimate and essential elements of urban ecology research. We argue in favor of theoretical and methodological pluralism. Rather than define urban ecology through exclusionary projects that would limit the scope and significance of urban ecology research, we reaffirm our call for diverse sets of actors inside and outside university settings to engage and support each other in order to develop and strengthen analysis and pursuit of sustainability.

Classroom approach for managing dietary restraint, negative eating styles, and body image concerns among college women

OBJECTIVE: In this exploratory study, the authors evaluated the impact of an elective college course on dieting levels, eating styles, and body image among college women. PARTICIPANTS: Participants were a convenience sample of 29 self-selected female students at a western university who were mostly white, normal-weight seniors with significant dieting experience. METHODS: The authors used valid and reliable instruments to collect data both before and after testing. An instructor conducted the program in an undergraduate course that met twice weekly for 15 weeks. Theory-based lessons focused on resisting media pressure, modifying dietary restraint, eating in response to hunger (intrinsic eating), and achieving healthy body image. Dependent variables included intrinsic eating, dieting involvement, emotional eating, body image, and self-esteem. RESULTS: A comparison of pretest and posttest scores identified significant improvements for most measures. CONCLUSIONS: A theory-driven elective course implemented within a college setting may improve women's eating styles and body image.     

Barriers and facilitators for walking in individuals with intermittent claudication

This study aimed to identify barriers and facilitators associated with walking for exercise among people who experience intermittent claudication. Fifteen individuals (7 men and 8 women) participated in 3 focus groups that were tape-recorded and content analyzed. A social-cognitive framework was used to categorize barriers and facilitators as those related to the person, to the activity, or to the environment. Variables identified included those specific to intermittent claudication and those common among the general population. Barriers to walking included irregular or graded walking surfaces, uncertainty about the outcome of walking, ambiguity regarding pain, the need to take rest breaks, and the presence of leg pain. Facilitating factors included availability of a resting place, use of cognitive coping strategies, companionship support, and availability of a treadmill-walking program. Findings are interpreted in light of current research on exercise determinants and encourage prospective examinations of the predictive validity of these factors for walking.     

Bayesian variable selection for proportional hazards models

The authors consider the problem of Bayesian variable selection for proportional hazards regression models with right censored data. They propose a semi-parametric approach in which a nonparametric prior is specified for the baseline hazard rate and a fully parametric prior is specified for the regression coefficients. For the baseline hazard, they use a discrete gamma process prior, and for the regression coefficients and the model space, they propose a semi-automatic parametric informative prior specification that focuses on the observables rather than the parameters. To implement the methodology, they propose a Markov chain Monte Carlo method to compute the posterior model probabilities. Examples using simulated and real data are given to demonstrate the methodology.     

Child-Focused Family Therapy: Behavioural Family Therapy Versus Brief Family Therapy

We examined the effectiveness of behavioural family therapy (following the treatment agenda outlined in Fleischman, Horne and Arthur, 1983) and brief family therapy (following the procedures outlined in Fisch, Weakland and Segal, 1985), in the treatment of child psychological disorders. The parents of the 49 children referred to the outpatient unit of a children's hospital completed the Child Behavior Checklist (CBCL) (Achenbach and Edelbrock, 1983). Three scales of the CBCL were examined to assess the effectiveness of the two therapeutic approaches pre- to post-treatment. Significant pre- and post-treatment differences were found for behavioural family therapy on the Internalizing, Externalizing, and Sum T scales and for brief family therapy on the Internalizing and Sum T scales. Sum T scales represent the sum of scores across all sub-scales of the CBCL. Neither treatment was found to be more effective than the other.     

Civilizing Northumberland: Representations of Englishness in the Tudor State

Taking Northumberland as a case study, this paper explores the wider implications of the Tudor strategy of reform by centralization, uniformity, and cultural imperialism. It reappraises the notion that the growth of centralized government at the expense of regional magnates was unambiguously a form of modernization; and argues that the essential character of the Tudor state and the radical nature of Tudor reform have been obscured by the historians' practice of viewing developments in terms of the rise of the nation.     

Issues with using baseline in last observation carried forward analysis

The topic of this paper was prompted by a study for which one of us was the statistician. It was submitted to Annals of Internal Medicine. The paper had positive reviewer comment; however, the statistical reviewer stated that for the analysis to be acceptable for publication, the missing data had to be accounted for in the analysis through the use of baseline in a last observation carried forward imputation. We discuss the issues associated with this form of imputation and recommend that it should not be undertaken as a primary analysis.