Statistical approaches for conducting network meta-analysis in drug development

We introduce health technology assessment and evidence synthesis briefly, and then concentrate on the statistical approaches used for conducting network meta-analysis (NMA) in the development and approval of new health technologies. NMA is an extension of standard meta-analysis where indirect as well as direct information is combined and can be seen as similar to the analysis of incomplete-block designs. We illustrate it with an example involving three treatments, using fixed-effects and random-effects models, and using frequentist and Bayesian approaches. As most statisticians in the pharmaceutical industry are familiar with SAS? software for analyzing clinical trials, we provide example code for each of the methods we illustrate. One issue that has been overlooked in the literature is the choice of constraints applied to random effects, and we show how this affects the estimates and standard errors and propose a symmetric set of constraints that is equivalent to most current practice. Finally, we discuss the role of statisticians in planning and carrying out NMAs and the strategy for dealing with important issues such as heterogeneity.     

Smoking risk factors and gender differences among Spanish high school students

The objectives of the present study were to analyze the pattern of tobacco use among Spanish adolescents, as well as to determine gender differences in specific risk factors of cigarette use. The study sample was made up of 1,483 boys and 1,358 girls, aged 12-16 (M = 14). Participants were asked to answer an ad-hoc instrument to evaluate the pattern of use, perceived availability, risk of harm, family- and peer-use, engagement in leisure activities, drive for thinness, and self-esteem. Results showed no gender differences in the pattern of use. With regard to risk and protector factors, a predictive analysis showed that peer-related variables were the most determinant for tobacco use both for boys and girls. Some gender differences were also detected: Playing sports was protective for boys only, and listening to music for girls only. Drive for thinness and self-esteem were not related to tobacco use for either boys or girls. These findings help increase our understanding of smoking risk factors in adolescence and to pay special attention to the group of friends when planning prevention programs to reduce risk factors.     

Social work and the shadow father: lessons for engaging fathers in Northern Ireland

The legislative framework of social work practice has consistently highlighted the need to work in partnership with parents, with far‐reaching implications for families. However, the importance of engaging fathers in social work practice is an issue that has received limited attention within academic debate and research. A research study undertaken across six family centres, investigated paternal involvement in family centre social work in Northern Ireland. The study involved 46 semi‐structured interviews with social workers, fathers and mothers. This paper presents the views of 22 social workers on the barriers to paternal involvement in family centre interventions. A range of factors were identified which served to inhibit or promote engagement of fathers. There were substantially more deterrents than promoters, a clear indicator of the problematic nature of paternal involvement. The findings highlight that both attitudes and practices of social workers influence the engagement of fathers. Recommendations drawn from the findings are presented for the development of father – inclusive social work practices and research.     

Hybrid-based confidence intervals for the ratio of two treatment means in the over-dispersed Poisson data

In many clinical trials and epidemiological studies, comparing the mean count response of an exposed group to a control group is often of interest. This type of data is often over-dispersed with respect to Poisson variation, and previous studies usually compared groups using confidence intervals (CIs) of the difference between the two means. However, in some situations, especially when the means are small, interval estimation of the mean ratio (MR) is preferable. Moreover, Cox and Lewis [4 D.R. Cox and P.A.W. Lewis, The Statistical Analysis of Series of Events, Methuen, London, 1966.[Crossref] , [Google Scholar]] pointed out many other situations where the MR is more relevant than the difference of means. In this paper, we consider CI construction for the ratio of means between two treatments for over-dispersed Poisson data. We develop several CIs for the situation by hybridizing two separate CIs for two individual means. Extensive simulations show that all hybrid-based CIs perform reasonably well in terms of coverage. However, the CIs based on the delta method using the logarithmic transformation perform better than other intervals in the sense that they have slightly shorter interval lengths and show better balance of tail errors. These proposed CIs are illustrated with three real data examples.     

Electricity consumption prediction with functional linear regression using spline estimators

A functional linear regression model linking observations of a functional response variable with measurements of an explanatory functional variable is considered. This model serves to analyse a real data set describing electricity consumption in Sardinia. The interest lies in predicting either oncoming weekends’ or oncoming weekdays’ consumption, provided actual weekdays’ consumption is known. A B-spline estimator of the functional parameter is used. Selected computational issues are addressed as well.     

Determinants of Interoutsourcing: An Analytical Approach

Interoutsourcing is a round‐way process in which the vendor is its customer's customer and the customer is its vendor's vendor. While interoutsourcing is emerging as a prominent outsourcing strategy in many industries, there are no rigorous analytical studies focusing on this mechanism. In this article, we analytically demonstrate the efficacy of interoutsourcing by comparing it with normal outsourcing. Our results show that, compared with normal outsourcing, interoutsourcing acts as a self‐enforcer of vendor firms' behaviors toward increasing outsourcing service value. However, in situations where there is a mismatch of outsourcing activities, a high degree of incentive that is based on outsourcing service value, and a high cost of capital, interoutsourcing is not preferred to normal outsourcing. We discuss these results in detail and provide managerial implications for firms involved in interoutsourcing decisions.     

Reversible jump methods for generalised linear models and generalised linear mixed models

A reversible jump algorithm for Bayesian model determination among generalised linear models, under relatively diffuse prior distributions for the model parameters, is proposed. Orthogonal projections of the current linear predictor are used so that knowledge from the current model parameters is used to make effective proposals. This idea is generalised to moves of a reversible jump algorithm for model determination among generalised linear mixed models. Therefore, this algorithm exploits the full flexibility available in the reversible jump method. The algorithm is demonstrated via two examples and compared to existing methods.     

Comparing quantile residual life functions by confidence bands

In this article we present a nonparametric method for constructing confidence bands for the difference of two quantile residual life (qrl) functions. These bands provide evidence for two random variables ordering with respect to the qrl order. The comparison of qrl functions is of importance, specially in the treatment of cancer when there exists a possibility of benefiting from a new secondary therapy. A qrl function is the quantile of the remaining life of a surviving subject, as it varies with time. We show the applicability of this approach in Medicine and Ecology. A simulation study has been carried out to evaluate and illustrate the performance and the consistency of this new methodology.