Examining the Reliability of Logistic Regression Estimation Software

Research Methods/ Statistical Methods,

A geophysical investigation of the south-east Greenland continental margin

During the summers of 1973 and 1974 geophysical observations were made, aboard R.R.S. Shackleton, across the south east Greenland continental margin, between 58 and 65 N. The thesis describes the reduction and interpretation of the magnetic, bathymetric, gravimetric, and deep seismic reflection data and gives details of the digital deconvolution and C.D.P. stacking techniques developed for processing the reflection data. The magnetic results indicate that, south of 63 N., anomaly 24 is the earliest recognisable oceanic magnetic anomaly. North of 63 N., anomalies 22-24 cut out against the margin, and a complementary widening of ocean floor of this age, on the opposite Rockall margin, north of Hatton Bank, indicates that a local westward migration of the spreading axis occurred, north of 63 N., shortly after the split. Igneous intrusives, outcropping on the rise, post-date the continental split by several million years, indicating that the volcanic activity of East Greenland may have occurred some time after continental separation started. Airgun and sparker profiles show three major sediment groups. Two groups of Tertiary age are separated by an erosional unconformity, beneath the rise north of 62 N. The upper sediments are interpreted as contour current deposits of Miocene and later age, and the lower sediments as lithified oozes of about Eocene age. Below these Tertiary sediments, older, seaward dipping reflectors occur between anomaly 24 and the scarp. These are interpreted as Mesozoic sediments overlying subsided continental crust. The oceanic-continental crustal boundary, as recognised from magnetic anomalies, occurs to the east of this subsided region and lies up to 80 km seaward of the scarp, which is an erosional feature cut by contour currents. Gravity profiles indicate that the main change in crustal thickness beneath the margin lies up to 80 km landward of the scarp north of 63.5 N; but corresponds more nearly with the scarp further south

Sample Size and Robustness of Inferences from Logistic Regression in the Presence of Nonlinearity and Multicollinearity

The logistic regression models has been widely used in the social and natural sciences and results from studies using this model can have significant impact. Thus, confidence in the reliability of inferences drawn from these models is essential. The robustness of such inferences is dependent on sample size. The purpose of this study is to examine the impact of sample size on the mean estimated bias and efficiency of parameter estimation and inference for the logistic regression model. A number of simulations are conducted examining the impact of sample size, nonlinear predictors, and multicollinearity on substantive inferences (e.g. odds ratios, marginal effects) and goodness of fit (e.g. pseudo-R2, predictability) of logistic regression models. Findings suggest that sample size can affect parameter estimates and inferences in the presence of multicollinearity and nonlinear predictor functions, but marginal effects estimates are relatively robust to sample size.Logistic Regression Model, Multicollinearity, Nonlinearity, Robustness, Small Sample Bias, Research Methods/ Statistical Methods,

A unified approach to the Clenshaw summation and the recursive computation of very high degree and order normalised associated Legendre functions

Spherical harmonic expansions form partial sums of fully normalised associated Legendre functions (ALFs). However, when evaluated increasingly close to the poles, the ultra-high degree and order (e.g. 2700) ALFs range over thousands of orders of magnitude. This causes existing recursion techniques for computing values of individual ALFs and their derivatives to fail. A common solution in geodesy is to evaluate these expansions using Clenshaw's method, which does not compute individual ALFs or their derivatives. Straightforward numerical principles govern the stability of this technique. Elementary algebra is employed to illustrate how these principles are implemented in Clenshaw's method. It is also demonstrated how existing recursion algorithms for computing ALFs and their first derivatives are easily modified to incorporate these same numerical principles. These modified recursions yield scaled ALFs and first derivatives, which can then be combined using Horner's scheme to compute partial sums, complete to degree and order 2700, for all latitudes (except at the poles for first derivatives). This exceeds any previously published result. Numerical tests suggest that this new approach is at least as precise and efficient as Clenshaw's method. However, the principal strength of the new techniques lies in their simplicity of formulation and implementation, since this quality should simplify the task of extending the approach to other uses, such as spherical harmonic analysis

Mary Douglas on Purity and Danger: An Interview

This interview with Mary Douglas took place at Lancaster University in the Religious Studies Department. The main focus of the interview was her recently published book, Purity and Danger, which had already become a classic of British anthropology. The questions and answers ranged mainly over the differences between the physical body, representations of the body, the body as a classificatory system, and social constructivism. Douglas’s early academic years and the influences on her work, such as the role of Roman Catholicism in her childhood and youth, were discussed. The interview concluded with speculation about the connections between anthropology and colonialism, and how she responded to those developments

Discourses of the War on Terror: Constructions of the Islamic Other in the wake of 7/7

It is widely agreed that the events which took place on 11 September 2001 have played a large part in reshaping global imaginings about contemporary acts of terrorism and their Islamic perpetrators. Given this transformation in the understanding of terrorism and terrorists, our objective in this article is threefold. First we want to present a discussion of the roots of the kind of neo-liberal politics that has grown up alongside acts of terrorism and its global media coverage which has, we argue, resulted in a politics of fear that acts to legitimate ever-increasing legislative controls. In an attempt to reveal how discourse works to support such regulation, in the second part of this article we offer a qualitative analysis of newspaper articles from the UK about acts of terrorism that have taken place since the suicide bombings on the London transport system on 7 July 2005. Together with an analysis of the political speeches of Bush and Blair, we examine how far these discourses can be said to have reframed notions of inclusion/exclusion for Muslim populations. Finally we present a discussion of the consequences of such terrorist acts and their varied representations for the future of the British multicultural imaginary

Farm Efficiency and Productivity Growth: The Effect of Commodity Prices

Crop prices can affect farm productivity through input- output decisions. This study assesses the relationship between crop prices and productivity changes among a sample of Kansas farms. The changes in total factor productivity are evaluated using a nonparametric approach with a Malmquist productivity index and potential drivers of technical efficiency and productivity change are analyzed. Farms with higher leverage and greater diversification are likely to be more efficient and experience productivity change. Lower productivity occurred during years with higher crop prices, suggesting that innovation is more likely to occur when margins are tight

The Divisive Power of Humour: Comedy, Taste and Symbolic Boundaries

Using British and Dutch interview data, this article demonstrates how people from different social classes draw strong symbolic boundaries on the basis of comedy taste. Eschewing the omnivorousness described in recent studies of cultural consumption, comedy audiences make negative aesthetic and moral judgements on the basis of comedy taste, and often make harsh judgements without the disclaimers, apologies and ambivalence so typical of ‘taste talk’ in contemporary culture. The article demonstrates how, in particular, Dutch and British middle class audiences use their comedy taste to communicate distinction and cultural superiority. We discuss several reasons why such processes of social distancing exist in comedy taste and not other cultural areas: the traditionally low status of comedy; the strong relation between humour and personhood; the continuity between comedy tastes and humour styles in everyday life; as well as the specific position of comedy in the British and Dutch cultural fields