2,980 research outputs found
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Exploration of a novel bootstrap technique for estimating the distribution of outstanding claims reserves in general insurance
This is a report on an exploration of the effectiveness of a novel non-parametric bootstrap method for estimating claims reserves, which we call the local chain ladder bootstrap technique. The method is simple and can readily be implemented in a spreadsheet. In addition analytic estimates of the first few moments of reserves are shown to the readily evaluated, obviating the need for simulation if desired. The behaviour of the method on three datasets is presented and compared to published predictions of some other stochastic methods. In addition, a small study of the method using simulated claims triangles is presented and compared with other stochastic models
Probabilistic expert systems for handling artifacts in complex DNA mixtures
This paper presents a coherent probabilistic framework for taking account of allelic dropout, stutter bands and silent alleles when interpreting STR DNA profiles from a mixture sample using peak size information arising from a PCR analysis. This information can be exploited for evaluating the evidential strength for a hypothesis that DNA from a particular person is present in the mixture. It extends an earlier Bayesian network approach that ignored such artifacts. We illustrate the use of the extended network on a published casework example
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Identification and separation of DNA mixtures using peak area information
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Identification and separation of DNA mixtures using peak area information (Updated version of Statistical Research Paper No. 25)
We introduce a new methodology, based upon probabilistic expert systems, for analysing forensic identification problems involving DNA mixture traces using quantitative peak area information. Peak area is modelled with conditional Gaussian distributions. The expert system can be used for ascertaining whether individuals, whose profiles have been measured, have contributed to the mixture, but also to predict DNA profiles of unknown contributors by separating the mixture into its individual components. The potential of our probabilistic methodology is illustrated on case data examples and compared with alternative approaches. The advantages are that identification and separation issues can be handled in a unified way within a single probabilistic model and the uncertainty associated with the analysis is quantified. Further work, required to bring the methodology to a point where it could be applied to the routine analysis of casework, is discussed
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A simple greedy algorithm for reconstructing pedigrees
This paper introduces a simple greedy algorithm for searching for high likelihood pedigrees using micro-satellite (STR) genotype information on a complete sample of related individuals. The core idea behind the algorithm is not new, but it is believed that putting it into a greedy search setting, and specifically the application to pedigree learning, is novel. The algorithm does not require age or sex information, but this information can be incorporated if desired. The algorithm is applied to human and non-human genetic data and in a simulation study
Estimation of Parameters in DNA Mixture Analysis
In Cowell et al. (2007), a Bayesian network for analysis of mixed traces of
DNA was presented using gamma distributions for modelling peak sizes in the
electropherogram. It was demonstrated that the analysis was sensitive to the
choice of a variance factor and hence this should be adapted to any new trace
analysed. In the present paper we discuss how the variance parameter can be
estimated by maximum likelihood to achieve this. The unknown proportions of DNA
from each contributor can similarly be estimated by maximum likelihood jointly
with the variance parameter. Furthermore we discuss how to incorporate prior
knowledge about the parameters in a Bayesian analysis. The proposed estimation
methods are illustrated through a few examples of applications for calculating
evidential value in casework and for mixture deconvolution
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When learning Bayesian networks from data, using conditional independence tests is equivalent to a scoring metric
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