Sample size re‐estimation incorporating prior information on a nuisance parameter

Prior information is often incorporated informally when planning a clinical trial. Here, we present an approach on how to incorporate prior information, such as data from historical clinical trials, into the nuisance parameter–based sample size re‐estimation in a design with an internal pilot study. We focus on trials with continuous endpoints in which the outcome variance is the nuisance parameter. For planning and analyzing the trial, frequentist methods are considered. Moreover, the external information on the variance is summarized by the Bayesian meta‐analytic‐predictive approach. To incorporate external information into the sample size re‐estimation, we propose to update the meta‐analytic‐predictive prior based on the results of the internal pilot study and to re‐estimate the sample size using an estimator from the posterior. By means of a simulation study, we compare the operating characteristics such as power and sample size distribution of the proposed procedure with the traditional sample size re‐estimation approach that uses the pooled variance estimator. The simulation study shows that, if no prior‐data conflict is present, incorporating external information into the sample size re‐estimation improves the operating characteristics compared to the traditional approach. In the case of a prior‐data conflict, that is, when the variance of the ongoing clinical trial is unequal to the prior location, the performance of the traditional sample size re‐estimation procedure is in general superior, even when the prior information is robustified. When considering to include prior information in sample size re‐estimation, the potential gains should be balanced against the risks.     

Split Hamiltonian Monte Carlo

We show how the Hamiltonian Monte Carlo algorithm can sometimes be speeded up by “splitting” the Hamiltonian in a way that allows much of the movement around the state space to be done at low computational cost. One context where this is possible is when the log density of the distribution of interest (the potential energy function) can be written as the log of a Gaussian density, which is a quadratic function, plus a slowly-varying function. Hamiltonian dynamics for quadratic energy functions can be analytically solved. With the splitting technique, only the slowly-varying part of the energy needs to be handled numerically, and this can be done with a larger stepsize (and hence fewer steps) than would be necessary with a direct simulation of the dynamics. Another context where splitting helps is when the most important terms of the potential energy function and its gradient can be evaluated quickly, with only a slowly-varying part requiring costly computations. With splitting, the quick portion can be handled with a small stepsize, while the costly portion uses a larger stepsize. We show that both of these splitting approaches can reduce the computational cost of sampling from the posterior distribution for a logistic regression model, using either a Gaussian approximation centered on the posterior mode, or a Hamiltonian split into a term that depends on only a small number of critical cases, and another term that involves the larger number of cases whose influence on the posterior distribution is small.     

Blinded continuous monitoring in clinical trials with recurrent event endpoints

In studies with recurrent event endpoints, misspecified assumptions of event rates or dispersion can lead to underpowered trials or overexposure of patients. Specification of overdispersion is often a particular problem as it is usually not reported in clinical trial publications. Changing event rates over the years have been described for some diseases, adding to the uncertainty in planning. To mitigate the risks of inadequate sample sizes, internal pilot study designs have been proposed with a preference for blinded sample size reestimation procedures, as they generally do not affect the type I error rate and maintain trial integrity. Blinded sample size reestimation procedures are available for trials with recurrent events as endpoints. However, the variance in the reestimated sample size can be considerable in particular with early sample size reviews. Motivated by a randomized controlled trial in paediatric multiple sclerosis, a rare neurological condition in children, we apply the concept of blinded continuous monitoring of information, which is known to reduce the variance in the resulting sample size. Assuming negative binomial distributions for the counts of recurrent relapses, we derive information criteria and propose blinded continuous monitoring procedures. The operating characteristics of these are assessed in Monte Carlo trial simulations demonstrating favourable properties with regard to type I error rate, power, and stopping time, ie, sample size.     

Correction to: The Impact of Agricultural Technologies on Poverty and Vulnerability of Smallholders in Ethiopia: A Panel Data Analysis

Social Indicators Research - The article The Impact of Agricultural Technologies on Poverty and Vulnerability of Smallholders in Ethiopia: A Panel Data Analysis, written by Wubneshe Dessalegn Biru,...     

The flavours of love: A cross‐cultural lexical analysis

Linguists have often remarked upon the polysemous nature of love, whereby the term encompasses a wide diversity of emotional relationships. Several typologies have been constructed to account for this diversity. However, these tend to be restricted in scope, and fail to fully represent the range of experiences signified by the term ‘love’ in discourse. In the interest of generating an expanded typology of love, encompassing its varied forms, an enquiry was conducted into relevant concepts found across the world's cultures, focusing on so‐called untranslatable words. Through a quasi‐systematic search of published and internet sources, 609 relevant words were identified. These were organised through a version of grounded theory into 14 categories, representing 14 different forms or ‘flavours’ of love. The result is an expanded theoretical treatment of love, allowing us to better appreciate the nuances of this most cherished and yet polysemous of concepts.     

Elite,exclusive and elusive: transgovernmental policy networks and iterative policy transfer in the Anglosphere

ABSTRACT

The prominent corridor of bilateral policy transfer between Australia and the UK is underpinned by a long-standing cultural and political proximity. While ad hoc cases of transfer have in recent years been the subject to concerted attention from transfer theorists, much less attention has been given to the rise of multilateral, or transgovernmental, policy networks based on similar cultural and political amity amongst the ‘Anglosphere’ group of states including Australia, Canada, New Zealand, the UK and the US. Populated by policy elites and regularly interacting, these networks represent potentially important modes of policy transfer yet little is known about how they operate, with what purposes or what outcomes. This article therefore sets out research findings that offer an insight into 23 identified networks, suggesting that understanding the emergence of these networks are crucial to explaining any bilateral transfer between Anglosphere states in general, and specifically Australia and the UK. The article contends that a consideration of these networks provides insight into (i) the substantive landscape of Anglosphere policy learning and collaboration, (ii) the attendant dynamics of collaborative policy networks as elite, elusive and exclusive and (iii) iterative policy transfers.     

所有产品都是利基品牌

什么是“利基品牌”（Niche brand）？作为美国斯巴鲁（Subaru）汽车公司的营销总监,我需要了解这个问题。斯巴鲁只占美国汽车市场份额的2％——显然,至少从数量上来讲,这就是一个利基市场。但数量本身还不足以说明问题。我认为,每个产品品牌都可以是利基品牌。人们绝对不会说,“我想买一辆通用（企业品牌）”,相反,他们会说,“我想买一辆雪佛兰”。     

Looking for a Grandview: introducing concepts of robust sampling to policymakers and practitioners engaged in measuring the well‐being of children at the local authority level

Local authorities are increasingly required to measure and monitor the well‐being of children. One key aspect of ensuring that these data on child well‐being are robust is that they form an accurate and representative picture of that child population. Rather than being only the purview of researchers, the act of gathering outcome data now falls within the remit of policymakers and practitioners. This article therefore describes the principles and importance of solid sampling methodologies to this audience and also considers the practical reasons as to why policymakers and practitioners may require larger samples than may be necessary for a representative picture of child well‐being. These ideas are illustrated by one local authority in the UK’s approach to measuring child well‐being, using representative sampling techniques and the subsequent expansion of this sample. The consequences of expanding the sample size are illustrated by examining the impact upon key findings related to child well‐being. The potential benefits and limitations of larger samples are discussed, as are some practical solutions to the apparent impasse.     

Reflexivity in the age of reconstructive social science

Calls to reflexivity in social science have a long history. This article, after defining the terms endogenous and referential reflexivity, examines that history within several traditions. It argues that this history has tended to prioritize endogenous over referential reflexivity through an over-emphasis on the process of social research compared to what is learnt about social relations. As a result, interactions within the social world and the potential for transformations are not adequately understood, nor are the relations between the social sciences and social life.