A small sample confidence interval for autoregressive parameters

This paper is concerned with interval estimation of an autoregressive parameter when the parameter space allows for magnitudes outside the unit interval. In this case, intervals based on the least-squares estimator tend to require a high level of numerical computation and can be unreliable for small sample sizes. Intervals based on the asymptotic distribution of instrumental variable estimators provide an alternative. If the instrument is taken to be the sign function, the interval is centered at the Cauchy estimator and a large sample interval can be created by estimating the standard error of this estimator. The interval proposed in this paper avoids estimating this standard error and results in a small sample improvement in coverage probability. In fact, small sample coverage is exact when the innovations come from a normal distribution.     

Re‐thinking Disability,Work and Welfare

There is a wealth of evidence that disabled people experience far higher levels of unemployment and underemployment than non‐disabled peers. Yet hitherto sociologists have paid scant attention to the structural causes of this issue. Drawing on a socio/political or social model of disability perspective this paper argues for a reconfiguration of the meaning of disability and work in order to address this problem. It is also suggested that such a strategy will make a significant contribution to the struggle for a fairer and equitable global society.     

The Contribution of Social Movement Theory to Understanding Terrorism

The study of terrorism and political violence has been characterized by a lack of generalizable theory and methodology. This essay proposes that social movement theory can contribute a necessary conceptual framework for understanding terrorism and thus reviews the relevant literature and discusses possible applications. Terrorism is a form of contentious politics, analyzable with the basic social movement approach of mobilizing resources, political opportunity structure, and framing. Cultural perspectives call attention to issues of collective identity that allow for sustained militancy, and movement research recommends alternative conceptions of terrorist networks. Previous research on movement radicalization, repression, and cycles of contention has direct bearing on militancy. Emerging perspectives on transnational collective action and the diffusion of tactics and issues informs an understanding of contemporary international terrorism. Research on movement outcomes suggests broader ways of considering the efficacy of political violence. Finally, methodological debates within the study of social movements are relevant for research on terrorism. In sum, a social movement approach to terrorism has much to contribute, and research on terrorism could have important extensions and implications for social movement theory.     

Sampling issues in the administration of justice

Colin Aitken first became interested in sampling in the context of the administration of justice when the case of US versus Shonubi was brought to his attention. Shonubi was a Nigerian working in New York. He was arrested at Kennedy Airport when seen behaving in a suspicious manner in the baggage hall, having returned on a flight from Nigeria. He was found to have 103 bags of a white substance inside him, four of which were examined. The white substance was identified as heroin. Shonubi was arrested, tried and found guilty of drug smuggling. The question then arose as to the length of sentence he should be given.     

Experience-weighted Attraction Learning in Normal Form Games

In ‘experience-weighted attraction’ (EWA) learning, strategies have attractions that reflect initial predispositions, are updated based on payoff experience, and determine choice probabilities according to some rule (e.g., logit). A key feature is a parameter δ that weights the strength of hypothetical reinforcement of strategies that were not chosen according to the payoff they would have yielded, relative to reinforcement of chosen strategies according to received payoffs. The other key features are two discount rates, φ and ρ, which separately discount previous attractions, and an experience weight. EWA includes reinforcement learning and weighted fictitious play (belief learning) as special cases, and hybridizes their key elements. When δ= 0 and ρ= 0, cumulative choice reinforcement results. When δ= 1 and ρ=φ, levels of reinforcement of strategies are exactly the same as expected payoffs given weighted fictitious play beliefs. Using three sets of experimental data, parameter estimates of the model were calibrated on part of the data and used to predict a holdout sample. Estimates of δ are generally around .50, φ around .8 − 1, and ρ varies from 0 to φ. Reinforcement and belief-learning special cases are generally rejected in favor of EWA, though belief models do better in some constant-sum games. EWA is able to combine the best features of previous approaches, allowing attractions to begin and grow flexibly as choice reinforcement does, but reinforcing unchosen strategies substantially as belief-based models implicitly do.     

Can personal budgets really deliver better outcome for all at no cost? Reviewing the evidence,costs and quality

Political recognition of the parlous state of English social care and the urgent need for radical reform led to calls for new policy approaches that address the two key problems it faced: inadequate funding and poor quality and inappropriate provision. The New Labour government was convinced that it had found a way of dealing with these two competing problems and it embarked on a policy, which has subsequently gained cross-party support. The centre-piece was the concept of a personal budget, and was introduced with a belief that there would be major cost savings while improving service user satisfaction. This article will critically explore the evidence for whether the strategy is fulfilling that promise.     

Automatic Bayesian quantile regression curve fitting

Quantile regression, including median regression, as a more completed statistical model than mean regression, is now well known with its wide spread applications. Bayesian inference on quantile regression or Bayesian quantile regression has attracted much interest recently. Most of the existing researches in Bayesian quantile regression focus on parametric quantile regression, though there are discussions on different ways of modeling the model error by a parametric distribution named asymmetric Laplace distribution or by a nonparametric alternative named scale mixture asymmetric Laplace distribution. This paper discusses Bayesian inference for nonparametric quantile regression. This general approach fits quantile regression curves using piecewise polynomial functions with an unknown number of knots at unknown locations, all treated as parameters to be inferred through reversible jump Markov chain Monte Carlo (RJMCMC) of Green (Biometrika 82:711–732, 1995). Instead of drawing samples from the posterior, we use regression quantiles to create Markov chains for the estimation of the quantile curves. We also use approximate Bayesian factor in the inference. This method extends the work in automatic Bayesian mean curve fitting to quantile regression. Numerical results show that this Bayesian quantile smoothing technique is competitive with quantile regression/smoothing splines of He and Ng (Comput. Stat. 14:315–337, 1999) and P-splines (penalized splines) of Eilers and de Menezes (Bioinformatics 21(7):1146–1153, 2005).     

If it didn't exist we'd have to invent it … Further reflections on the ontological status of the state

In this brief response to Bob Jessop's probing yet sympathetic critique, I clarify further the ‘as if realist’ political ontology of the state. I suggest that critical realism's appeal to the ontological stratification of social reality and to the logic of retroduction are the principal stumbling blocks for ‘as if realists’, that the appeal to state power(s) as distinct from the state as real cannot circumvent the ‘as if realist’ ontological objection to the state as real since both remain conceptual abstractions, but that there is a natural affinity between the strategic‐relational approach developed by Jessop and others and the ‘as if realist’ ontology of the state that I here elucidate.