Results 1  10
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14
The Pollution Content of
 American Trade.Western Economic Journal
, 1973
"... Prepared in cooperation with the ..."
Line Transect Methods for Plant Surveys
"... SUMMARY. Interest in surveys for monitoring plant abundance is increasing, due in part to the need to quantify the rate of loss of biodiversity. Line transect sampling offers an efficient way to monitor many species. However, the method does not work well in some circumstances, for example on small ..."
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SUMMARY. Interest in surveys for monitoring plant abundance is increasing, due in part to the need to quantify the rate of loss of biodiversity. Line transect sampling offers an efficient way to monitor many species. However, the method does not work well in some circumstances, for example on small survey plots, when the plant species has a strongly aggregated distribution, or when plants that are on the line are not easily detected. We develop a crossed design, together with methods that exploit the additional information from such a design, to address these problems. The methods are illustrated using data on a colony of cowslips.
Simultaneous adjustment of bias and coverage probabilities for confidence intervals
, 2014
"... A new method is proposed for the correction of confidence intervals when the original interval does not have the correct nominal coverage probabilities in the frequentist sense. The proposed method is general and does not require any distributional assumptions. It can be applied to both frequentist ..."
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A new method is proposed for the correction of confidence intervals when the original interval does not have the correct nominal coverage probabilities in the frequentist sense. The proposed method is general and does not require any distributional assumptions. It can be applied to both frequentist and Bayesian inference where interval estimates are desired. We provide theoretical results for the consistency of the proposed estimator, and give two complex examples, on confidence interval correction for composite likelihood estimators and in approximate Bayesian computation (ABC), to demonstrate the wide applicability of the new method. Comparison is made with the doublebootstrap and other methods of improving confidence interval coverage.
Spatial Distance Sampling Modeling of Cetaceans Observed from Platforms of
, 2005
"... In this paper I outline the standard methods of distance sampling and how they are used to obtain estimates of density and abundance for species of interest. I then develop these methods following the approach of Hedley (2000) whereby waiting distances between detections are modelled to produce a de ..."
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In this paper I outline the standard methods of distance sampling and how they are used to obtain estimates of density and abundance for species of interest. I then develop these methods following the approach of Hedley (2000) whereby waiting distances between detections are modelled to produce a density map of the area of interest. In doing so Standard distance sampling, multicovariate distance sampling and generalized additive models are all discussed and combined together to achieve the density surface. The methods presented are then applied to a data set of fin whale provided by the Biscay Dolphin Research Programme (BDRP). Using the spatial model produced their a priori beliefs on the location of fin whale and trends in numbers are assessed. Both the density map produced (showing locations of high densities) and within season abundance estimates (together with 95 % confidence intervals) support the claims set out by the BDRP.
EDITORIAL ASSISTANCE
"... STUDY This document was requested by the European Parliament's Committee on Committee on ..."
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STUDY This document was requested by the European Parliament's Committee on Committee on
© 2001 Kluwer Academic Publishers. Printed in the Netherlands. Research Article Analysis and simulation of landuse change in the central Arizona –
"... To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the landuse pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exp ..."
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To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the landuse pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exponentially for the past 83 years, and this urban expansion is correlated with the increase in population size for the same period of time. The accelerating urbanization process has increased the degree of fragmentation and structural complexity of the desert landscape. To simulate landuse change we developed a Markovcellular automata model. Model parameters and neighborhood rules were obtained both empirically and with a modified genetic algorithm. Landuse maps for 1975 and 1995 were used to implement the model at two distinct spatial scales with a time step of one year. Model performance was evaluated using MonteCarlo confidence interval estimation for selected landscape pattern indices. The coarsescale model simulated the statistical patterns of the landscape at a higher accuracy than the finescale model. The empirically derived parameter set poorly simulated landuse change as compared to the optimized parameter set. In summary, our results showed that landscape pattern metrics (patch density, edge density, fractal dimension, contagion) together were able to effectively capture the trend in landuse associated with urbanization for this region. The Markovcellular automata parameterized by a modified genetic algorithm reasonably replicated the change in landuse pattern.
Internal External Examiner
, 2003
"... ii Capturerecapture, or multilist methods, are used by investigators to estimate the unknown size of a target population whose size cannot be reasonably enumerated. This thesis presents three new methods to estimate population sizes when lists are only partially available or where there is incompl ..."
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ii Capturerecapture, or multilist methods, are used by investigators to estimate the unknown size of a target population whose size cannot be reasonably enumerated. This thesis presents three new methods to estimate population sizes when lists are only partially available or where there is incomplete information available regarding individuals on lists. These methods can assist with population estimation problems occurring in technological, ecological and biological sciences, as well as in epidemiological and public health settings. First, stratification of lists has often been used to reduce the biases caused by heterogeneity in the probability of list membership among members of a target population. A method is developed to deal with cases when not all lists are active in all strata. Using a loglinear modelling framework, list dependencies and differential probabilities of ascertainment are incorporated. The methodology uses an EM algorithm and is applied to three examples; estimating the number of people with
Research Article Analysis and simulation of landuse change in the central Arizona –
"... To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the landuse pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exp ..."
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To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the landuse pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exponentially for the past 83 years, and this urban expansion is correlated with the increase in population size for the same period of time. The accelerating urbanization process has increased the degree of fragmentation and structural complexity of the desert landscape. To simulate landuse change we developed a Markovcellular automata model. Model parameters and neighborhood rules were obtained both empirically and with a modified genetic algorithm. Landuse maps for 1975 and 1995 were used to implement the model at two distinct spatial scales with a time step of one year. Model performance was evaluated using MonteCarlo confidence interval estimation for selected landscape pattern indices. The coarsescale model simulated the statistical patterns of the landscape at a higher accuracy than the finescale model. The empirically derived parameter set poorly simulated landuse change as compared to the optimized parameter set. In summary, our results showed that landscape pattern metrics (patch density, edge density, fractal dimension, contagion) together were able to effectively capture the trend in landuse associated with urbanization for this region. The Markovcellular automata parameterized by a modified genetic algorithm reasonably replicated the change in landuse pattern.
ComputerIntensive Statistics
 APTS 2012–13 LECTURE MATERIAL
, 2012
"... ‘Computerintensive statistics’ is statistics that could only be done with ‘modern‘ computing resources, typically either • Statistical inference on small problems which needs a lot of computation to do at all, or to do well. Quite small datasets can need complex models to explain, and even simple m ..."
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‘Computerintensive statistics’ is statistics that could only be done with ‘modern‘ computing resources, typically either • Statistical inference on small problems which needs a lot of computation to do at all, or to do well. Quite small datasets can need complex models to explain, and even simple models can need a lot of computation for a realistic analysis (especially where dependence is involved). • Statistical inference on ‘huge ’ problems. All of these terms are relative and change quite rapidly—according to the most commonly quoted version of Moore’s Law (see section 6 and Ripley (2005)) computing power will quadruple during your doctoral studies. One very important idea for doing statistical inference ‘well ’ on analytically intractable statistical models (that is, most realworld ones) is to make use of simulation. So most of this module could be subtitled simulationbased inference, as in Geyer (1999)’s comments about MCMC for spatial point processes: If you can write down a model, I can do likelihood inference for it, not only maximum