Bayesian inference for non-stationary spatial covariance structure via spatial deformations

Summary. In geostatistics it is common practice to assume that the underlying spatial process is stationary and isotropic, i.e. the spatial distribution is unchanged when the origin of the index set is translated and under rotation about the origin. However, in environmental problems, such assumptions are not realistic since local influences in the correlation structure of the spatial process may be found in the data. The paper proposes a Bayesian model to address the anisot- ropy problem. Following Sampson and Guttorp, we define the correlation function of the spatial process by reference to a latent space, denoted by D , where stationarity and isotropy hold. The space where the gauged monitoring sites lie is denoted by G . We adopt a Bayesian approach in which the mapping between G and D is represented by an unknown function d (·). A Gaussian process prior distribution is defined for d (·). Unlike the Sampson–Guttorp approach, the mapping of both gauged and ungauged sites is handled in a single framework, and predictive inferences take explicit account of uncertainty in the mapping. Markov chain Monte Carlo methods are used to obtain samples from the posterior distributions. Two examples are discussed: a simulated data set and the solar radiation data set that also was analysed by Sampson and Guttorp.     

The Elephant Man (David Lynch, EMI Films, 1980): An Analysis from a Disabled Perspective

A paper that uses Foucault's ideas on normalisation and medicalisation to discuss David Lynch's The Elephant Man as a movie that dehumanises and objectifies its subject rather than one that represents abnormality/disability as human or valid in itself, as it is often claimed for the film. I analyse the methods by which the film inadvertently portrays the historical process of medicalisation and reinforces its ideology of normality as 'common sense' and abnormality as inhuman and 'unbearable' due to its pathological state rather than social construction; with the 'Freak'/abnormality (as carnivalesque) also being examined. I consequently analyse the ambiguities of the film to show its hidden agenda (through unconscious acceptance) of placing abnormality further and further into the realms of the Other, with eugenic overtones.     

Sequential Parimutuel Betting in the Laboratory

This paper investigates parimutuel betting in the laboratory. Our experimental design relies on a simple sequential betting game where equilibrium strategies are characterized according to objective probabilities, the number of bettors, and publicly observable odds. The empirically well-documented phenomenon referred to as the favorite-longshot bias is observed in two of our three treatments. We offer a theoretical explanation of the subjects' behavior which relies on rank-dependent expected utility and pessimistic expectations about future bets.     

Robust and diagnostic regression analyses

Graphical methods of diagnostic regression analysis are applied to three examples in which least squares and robust regression analyses give substantially different results. The diagnostic tools lead to the identification of data deficiencies and model inadequacies. The analyses serve as a reminder that robust regressions depend upon the linear model and upon the scale in whicli the response is analysed. The robust analysis may also be sensitive to gross errors in one or more explanatory variables     

Asymptotic properties of bivariate k-means clusters

A bounded region in R² with a uniform density function defined over it is partitioned into k sub-regions such that the within cluster sum of squares is minimized. An asymptotic (k+∞) lower bound for the within cluster sum of squares of this optimal k-means partition is obtained. This lower bound is useful in suggesting that the graph-configuration of the optimal k-partition would consist of regular hexagons of equal size when k is large enough. An empirical study illustrating these asymptotic properties of blvariate k-means cluster is also presented.     

Implementation of recursive nonparametric kernel estimation and a monte carlo study on its finite sample properties

The recursive estimator for the conditional mean of a nonparametric regression model with independent observations was thoroughly explored by Ahmad and Lin (1976), and Singh and Ullah (1986). Their studies are mainly concerned with the estimator's asymptotic behaviour. However, they do not include much discussion on the strategy of computing the estimates. In this paper, we provide a convenient implementation of the recursive estimator and examine its finite sample properties through simulation studies. Our study has demonstrated that for relatively short length of recursive updating, the estimates are generally equivalent to their fixed window width counterparts However, we found that substantial recursive updating can seriously lower the estimator's efficiency even though it is a consistent estimator.     

Regression analysis with partially labelled regressors: carbon dating of the Shroud of Turin

The twelve results from the 1988 radio carbon dating of the Shroud of Turin show surprising heterogeneity. We try to explain this lack of homogeneity by regression on spatial coordinates. However, although the locations of the samples sent to the three laboratories involved are known, the locations of the 12 subsamples within these samples are not. We consider all 387,072 plausible spatial allocations and analyse the resulting distributions of statistics. Plots of robust regression residuals from the forward search indicate that some sets of allocations are implausible. We establish the existence of a trend in the results and suggest how better experimental design would have enabled stronger conclusions to have been drawn from this multi-centre experiment.     

Stability of Approximations of Average Run Length of Risk-Adjusted CUSUM Schemes Using the Markov Approach: Comparing Two Methods of Calculating Transition Probabilities

Risk-adjusted CUSUM schemes are designed to monitor the number of adverse outcomes following a medical procedure. An approximation of the average run length (ARL), which is the usual performance measure for a risk-adjusted CUSUM, may be found using its Markov property. We compare two methods of computing transition probability matrices where the risk model classifies patient populations into discrete, finite levels of risk. For the first method, a process of scaling and rounding off concentrates probability in the center of the Markov states, which are non overlapping sub-intervals of the CUSUM decision interval, and, for the second, a smoothing process spreads probability uniformly across the Markov states. Examples of risk-adjusted CUSUM schemes are used to show, if rounding is used to calculate transition probabilities, the values of ARLs estimated using the Markov property vary erratically as the number of Markov states vary and, on occasion, fail to converge for mesh sizes up to 3,000. On the other hand, if smoothing is used, the approximate ARL values remain stable as the number of Markov states vary. The smoothing technique gave good estimates of the ARL where there were less than 1,000 Markov states.     

The globalization of production,national labour regulations and income inequality in the global North and South, 1980–2013

A central concern over global value chains (GVCs) is whether the integration of national firms into GVCs exacerbates income inequality within countries. However, despite decades of research, the distributional consequences of GVCs remain unclear in the empirical literature. Drawing on panel data from 96 countries between 1980 and 2013, we examine the effects of GVC integration on market income inequality and whether national labour regulations moderate these effects. We find integration increases inequality in the global North and South. More importantly, we find labour regulations amplify the inequality effects of integration in Southern countries by expanding the size of the informal sector while suppressing these effects in Northern countries by promoting unionization. This suggests institutional power from national labour regulations may enhance the bargaining power of labour in the North through increasing collective resources while disempowering labour in the South through reinforcing labour market segmentation between formal and informal sectors.