A method for Bayesian regression modelling of composition data

Many scientific and industrial processes produce data that is best analysed as vectors of relative values, often called compositions or proportions. The Dirichlet distribution is a natural distribution to use for composition or proportion data. It has the advantage of a low number of parameters, making it the parsimonious choice in many cases. In this paper we consider the case where the outcome of a process is Dirichlet, dependent on one or more explanatory variables in a regression setting. We explore some existing approaches to this problem, and then introduce a new simulation approach to fitting such models, based on the Bayesian framework. We illustrate the advantages of the new approach through simulated examples and an application in sport science. These advantages include: increased accuracy of fit, increased power for inference, and the ability to introduce random effects without additional complexity in the analysis.Comment: 10 pages, 1 figure, 2 table

e-Democracy driven by civil society: Developing a theoretical basis to design for bottom-up participation

This short paper outlines initial ideas for a programme of research related to e-Democracy which commences in October 2008 and will be undertaken over the next three years. The research specifically intends to focus on factors in the architecture of online discursive spaces which may affect sustained and meaningful participation. It begins by describing the context as it relates to Community Informatics (CI). It then outlines the nature of one of the online communities that will be at the centre of the enquiry. Finally, it outlines four theoretical perspectives which seem to offer a route to analysis and sense-making, suggesting how a synthesis of these perspectives might contribute to original insights for CI

Modern Application of the Roman Institution of fiducia cum creditore contracta

This is a preprint of a piece that appeared in Letitia Vacca, ed., La Garanzia nella prospettiva storico-comparatisca (Torino, 2003), pp. 327-44.The author illustrates the modern application of the Roman fiducia cum creditore contracta by reference to the South African case of Nedcor Bank Ltd v Absa Bank Ltd 1998 2 SA 830 (W)

The Distribution of Ownership in an Apartment Ownership or Condominium Scheme

This is a preprint of an article that appeared in: 2002 Georgia Journal of International and Comparative Law, pp. 101-37

Direct deliberative local governance using online media – consensual problem solving or a recalcitrant pluralism?

This paper describes and analyses distinct patterns of 'governance conversation' observed in interactions on a discussion list that aims to support local, direct, governance in a geographically colocated community in South Africa. Although each pattern relates to governance, making 'binding decisions', which has been seen as a key attribute of deliberative democratic processes, is almost entirely absent from the observed interactions. Nonetheless, the exchanges appear to be relevant and useful to the broader process of local direct deliberative governance. We investigate the extent to which the patterns feature instrumental or expressive dialogue, and subsequently support consensual or pluralist outcomes. The results propose that online interaction is particularly suited to facilitating the pluralist deliberation required to manage complex local governance problems. The outcomes observed in the case study further suggest the potential value of an infrequently investigated context of online deliberation – that of citizen-to-citizen deliberation of geographically local issues; and presents a broader conception of the role of online deliberation in local governance, where formal decision making is frequently over privileged in research

The impact of environmental resources on the stress process : encouraging positive outcomes in the workplace : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University, Turitea, New Zealand

The present study investigated resources in the organisational environment which would increase the likelihood of positive outcomes from the stress process. 120 Participants from a large New Zealand organisation filled out an on-line questionnaire assessing demands, primary appraisals, coping strategies and positive and negative stress outcomes. The organisational resources of control, role clarity, peer relations and leader relations were also measured. Bivariate correlations indicated that control, role clarity, peer and leader relations were all associated with increased positive stress outcomes and decreased negative outcomes. Multiple regression analysis suggested that environmental resources affected stress outcomes in a positive way by mediating the relationship between demands and challenge appraisals, as well as by directly increasing the likelihood of more effective coping strategies

Numerus Clausus and the Development of New Real Rights in South Africa

This is a preprint of an article that appeared in: 2002 South African Law Journal 803-15.This paper provides a general background to the development of real rights in South Africa, provides illustrations of the recognition of new real rights within the traditional categories, and suggests how the present problem can be clarified

Hospital benchmarking analysis and the derivation of cost indices

This paper reports work undertaken for the UK Department of Health to explore approaches to measuring and comparing hospital productivity. The purpose of the cost indices produced in this paper has been to use them to derive productivity scores for English NHS Trusts in order to benchmark them against one another to help identify poorer performers. The work builds on previous deterministic ‘efficiency indices’ by using statistical regression adjustment techniques. This work describes the derivation of three cost indices (CCI, 2CCI and 3CCI), each with increasing adjustment in terms of case mix, factor prices and environmental factors. The analysis uses data for the year 1995/6 and specifically examines acute Trusts. The CCI cost index is a deterministic index that takes into account case mix as measured by Healthcare Resource Groups (HRGs) and inpatient, first outpatient and accident and emergency (A & E) activity. It is a weighted index of actual / expected costs where expected costs are measured as average national costs per respective attendance. 2CCI takes factors into account such as additional adjustments for case mix, age and gender mix, transfers in and out of the hospital, inter-specialty transfers, local labour and capital prices and teaching and research costs for which Trusts might be over or under compensated. The 3CCI makes additional adjustments over and above those in the 2CCI for hospital capacity, including number of beds, and number of sites, scale of inpatient and non-inpatient activity and scope of activity. It therefore tries to capture institutional characteristics amenable to change in the long, but not the short run. 2CCI and 3CCI indices are obtained from a short-run regression model using CCI as the dependent variable, and productivity scores are obtained from the residuals of the regressions. The results suggest that the statistical adjustments reduce estimates of productivity variation between providers considerably, such that there is relatively little difference between providers in terms of fully adjusted (short-run) productivity scores (3CCI). This suggests that savings from bringing poorer performers up to those with higher productivity scores, may in fact be quite small. In the long run there may be more scope for productivity enhancement and savings than in the short run, by optimising capacity and activity levels. Productivity benchmarking results should always be tempered against judgements on the quality and effectiveness of service provision which these indices are currently unable to measure. Implicitly equating high cost to inefficiency, as these indices do, may also be problematic. The paper suggests that the use of panel data and the application of alternative methodologies (such as stochastic frontiers and Data Envelopment Analysis) would be a valuable way to extend this work.cost index, productivity

GPS analysis of a team competing in a national under 18 field hockey tournament

The purpose of this study was to utilise global-positioning system (GPS) technology to quantify the running demands of national under 18 field hockey players competing in a regional field hockey tournament. Ten male field hockey players (mean ± SD; age 17.2 ± 0.4 years; stature 178.1 ± 5.2 cm; body mass 78.8 ± 8.8 kg) playing in different positional groups as strikers, midfielders and defenders wore GPS units while competing in six matches over seven days at an under 18 national field hockey tournament. GPS enabled the measurement of total distance (TD), low-speed activity (LSA; 0 -14.9 km/hr), and high-speed running (HSR; ≥ 15 km/hr) distances in addition to distances over five velocity bands (≤ 5.9km.h-1; 6 – 10km.h-1; 10.1 – 14.9km.h-1; 15 – 24.6km.h-1; and ≥ 24.7km.h-1). Midfielders covered significantly higher TD and the highest LSA when compared to other positional groups. Strikers covered significantly higher HSR and the lowest LSA out of all positional groups. These results suggest that these playing positions are sufficiently different to warrant specialised position-specific conditioning training leading into a field hockey tournament. Therefore, training schedules, substitutions and intra-match recovery should be tailored by position, taking into account the needs of the individual players