A stepwise algorithm for selecting category boundaries for the chi-squared goodness-of-fit test

A stepwise algorithm for selecting categories for the chisquared goodness-of-fit test with completely specified continuous null and alternative distributions is described in this paper. The procedure's starting point is an initial partitioning of the sample space into a large number of categories. A second partition with one fewer category is constructed by combining two categories of the original partition. The procedure continues until there are only two categories; the partition in the sequence with the highest estimated power is the one chosen. For illustartive purposes, the performance of the algorithm is evaluated for several hypothesis tests of the from H₀: normal distribution vs. H₁: a specific mixed normal distribution. For each test considered, the partition identified by the algorithm was compared to several equiprobable partitions, including the equiprobable partition with the highest estimated power. In all cases but one, the algorithm identified a parttion with higher estimated power than the best equiprobable partition. Applciations of the procedure are discussed.     

Costing Mixed Coxian Phase-type Systems with Poisson Arrivals

Previously, we developed a modeling framework which classifies individuals with respect to their length of stay (LOS) in the transient states of a continuous-time Markov model with a single absorbing state; phase-type models are used for each class of the Markov model. We here add costs and obtain results for moments of total costs in (0, t], for an individual, a cohort arriving at time zero and when arrivals are Poisson. Based on stroke patient data from the Belfast City Hospital we use the overall modelling framework to obtain results for total cost in a given time interval.     

An Extended Mixture Distribution Survival Tree for Patient Pathway Prognostication

Mixture distribution survival trees are constructed by approximating different nodes in the tree by distinct types of mixture distributions to improve within node homogeneity. Previously, we proposed a mixture distribution survival tree-based method for determining clinically meaningful patient groups from a given dataset of patients’ length of stay. This article extends this approach to examine the interrelationship between length of stay in hospital, outcome measures, and other covariates. We describe an application of this approach to patient pathway and examine the relationship between length of stay in hospital and/or treatment outcome using five-years’ retrospective data of stroke patients.     

Book Review: Michael Edwards and Alan Fowler (eds.), The Earthscan Reader on NGO Management,Earthscan, London, 2002, 455 pp., notes,index, $18.95

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -     

Coastal settlement patterns and exposure to sea-level rise in the Jaffna Peninsula,Sri Lanka

The Jaffna Peninsula in Sri Lanka has a generally flat topography with a median elevation of 2.72 m, and thus faces a high risk from sea-level rise that has the potential to have adverse impacts on the livelihoods of coastal communities. Understanding these risks and identifying the regions that could be adversely impacted is critical for planning future settlements and developing preventative protocols where possible. The aim of this study was to analyze the exposure of coastal settlements of the Jaffna Peninsula to climate risks, particularly to sea-level rise, and to identify the areas that are likely to be impacted under different sea-level rise scenarios. Raster-based sea-level rise modeling was performed with a digital elevation model produced with topographic contours and spot heights. The spatial distribution of individual residential houses for the entire Jaffna Peninsula was obtained through manual digitization using virtual globe platforms and high-resolution satellite images, and the houses exposed to inundation under various Representative Concentration Pathways from 2025 to 2100 were identified. The results showed that a majority (55.5%) of the residential buildings in the Jaffna Peninsula are located within 3 m above sea level. Approximately 5554 (5.6%) of the houses were projected to be inundated by 2100, and this projection increased to approximately 25,074 (25.4%) under high tide scenarios. This study highlights the coastal communities with a high level of exposure to coastal inundation where adaptation planning is essential. These results provide insights for coastal managers and policy makers for future planning of new settlements and urban expansion.

     

Comparative performance of tests of normality in detecting mixtures of parallel regression lines

This paper addresses the problem of detecting a mixture of parallel regression lines when information about group member¬ship of individual cases is not given. The problem is approached as a missing variable problem, with the missing variables being the dummy variables that code for groups. If a mixture of par¬allel regression lines with normally distributed error terms is present, a simple regression model without dummy variables will produce residuals that follow approximately a mixed normal dis¬tribution. In a simulation studyr several goodness-of-fit tests of normality were used to test the residuals obtained from mis-specified models that excluded dummy variables, Factors varied in the simulation included the number and the separation of the parallel lines and the sample size, The goodness-of-fit test based on the sample kurtosis (82) was overall most powerful in detecting mixtures of parallel regression lines, Applications are discussed.