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Biomedical subjects

A P Dawid

Publications and source records attributed to A P Dawid.

8 recordsLinked to original sources
PubMed2006

Object-oriented Bayesian networks for complex forensic DNA profiling problems.

We describe a flexible computational toolkit, based on object-oriented Bayesian networks, that can be used to model and solve a wide variety of complex problems of relationship testing using DNA profiles. In particular this can account for such complicating features as missing individuals, mutation and null alleles. We illustrate the use of this toolkit with several examples, including disputed paternity with missing or additional measurements, and criminal identification. We investigate the effects on likelihood ratios of introducing mutation and/or null alleles, and show that this can be substantial even when the underlying perturbations are small.

Bayes Theorem↗
PubMed2004

A statistical treatment of biases affecting the estimation of mutation rates.

We consider the estimation of mutation rates, using family data obtained from disputed paternity cases. It is shown how to take appropriate account of a number of complicating features-in particular, hidden mutation, differential mutation, and uncertain paternity-which can necessitate large corrections to simple estimates.

Alleles↗
PubMed2003

Probabilistic expert systems for DNA mixture profiling.

We show how probabilistic expert systems can be used to structure and solve complex cases of forensic identification involving DNA traces that might be mixtures of several DNA profiles. In particular, this approach can readily handle cases where the number of contributors to the mixture cannot be regarded as known in advance. The flexible modularity of the networks used also allows us to handle still more complex cases, for example where the finding of a mixed DNA trace is compounded by such features as missing individuals or the possibility of unobserved alleles.

Alleles↗
PubMed2001

Non-fatherhood or mutation? A probabilistic approach to parental exclusion in paternity testing.

The occurrence of germline mutations at microsatellite loci poses problems in ascertaining non-fatherhood status in paternity testing. We describe the appropriate probabilistic analysis for computing the likelihood ratio in favour of paternity while allowing for mutation, for all 18 relevant combinations of seemingly incompatible parental genotypes. We allow arbitrary and possibly different mutation rates in paternal and maternal germlines. We describe a stationary mutation model for expressing the required allele-specific transition mutation rates in terms of overall mutation rates, and compare the likelihood ratios calculated from this and from other mutation models suggested in the literature. We also show how to derive an upper bound on the likelihood ratio, depending only on the overall mutation rate.

Female↗
PubMed1976

Properties of diagnostic data distributions.

In applications of statistical methods to medical diagnosis, information on patients' diseases and symptoms is collected and the resulting data-base is used to diagnose new patients. The data-structure is complicated by a number of factors, two of which are examined here: selection bias and unstable population. Under reasonable conditions, no correction for selection bias is required when assessing probabilities for diseases based on symptom information, and it is suggested that these "diagnostic distributions" should form the principal object of study. Transformation of these distributions under changing population structure is considered and shown to take on a simple form in many situations. It is argued that the prevailing paradigm of diagnostic statistics, which concentrates on incidence of symptoms for given disease, is largely inappropriate and should be replaced by an emphasis on diagnostic distributions. The generalized logistic model is seen to fit naturally into the new framework.

Biometry↗