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Wing K Fung

Publications and source records attributed to Wing K Fung.

11 recordsLinked to original sources
PubMed2003

Median regression for longitudinal data.

We review and compare three estimators of median regression in linear models with longitudinal data. The estimators are constructed based on well-known ideas of weighting, decorrelating, and the working assumption of independence. Both asymptotic efficiency calculations and finite-sample Monte Carlo studies are used to assess the performance of these estimators. We find that their relative performances depend on the nature of covariates. The estimator under the working assumption of independence is computationally simple and yet has good relative performance when the covariates are invariant over time or when the within-subject correlations are small. Its relative performance in finite samples is also found to be more favourable than suggested by the asymptotic comparisons.

Analgesics↗
PubMed2003

User-friendly programs for easy calculations in paternity testing and kinship determinations.

Four computer programs are developed for easy calculations of likelihood ratios (LRs) for paternity testing and kinship determinations. The programs are constructed based on the concepts of Bayes Theorem, conditional probability and pedigree analysis. Computer enumeration is used for handling the calculations. The programs have wide applicability, and users can save and check the results easily. The programs employ the distinctive pull-down manual, making them very easy to use. In this paper, we explain the theory and describe various features of the software.

Alleles↗
PubMed2003

Testing for kinship in a subdivided population.

The effect of population subdivision on the determination of kinship of any two persons is investigated in this paper. Expressions of the joint genotype probabilities and likelihood ratios on kinship testing are reported. Two real cases are analysed using the Hong Kong Chinese population data and the Spanish data. Various kinds of relationships are investigated for illustration.

Child↗
PubMed2003

Evaluating forensic DNA mixtures with contributors of different structured ethnic origins: a computer software.

The effect of a structured population on the likelihood ratio of a DNA mixture has been studied by the current authors and others. In practice, contributors of a DNA mixture may belong to different ethnic/racial origins, a situation especially common in multi-racial countries such as the USA and Singapore. We have developed a computer software which is available on the web for evaluating DNA mixtures in multi-structured populations. The software can deal with various DNA mixture problems that cannot be handled by the methods given in a recent article of Fung and Hu.

Alleles↗
PubMed2003

Analyzing hospital length of stay: mean or median regression?

BACKGROUND: Length of stay (LOS) is an important measure of hospital activity and health care utilization, but its empirical distribution is often positively skewed. OBJECTIVE: This study reviews the mean and median regression approaches for analyzing LOS, which have implications for service planning, resource allocation, and bed utilization. METHODS: The two approaches are applied to analyze hospital discharge data on cesarean delivery. Both models adjust for patient and health-related characteristics, and for the dependency of LOS outcomes nested within hospitals. The estimation methods are also compared in a simulation study. RESULTS: For the empirical application, the mean regression results are somewhat sensitive to the magnitude of trimming chosen. The identified factors from median regression, namely number of diagnoses, number of procedures, and payment classification, are robust to high-LOS outliers. The simulation experiment shows that median regression can outperform mean regression even when the response variable is moderately positively skewed. CONCLUSION: Median regression appears to be a suitable alternative to analyze the clustered and positively skewed LOS, without transforming and trimming the data arbitrarily.

Cesarean Section↗
PubMed2002

Evaluating mixed stains with contributors of different ethnic groups under the NRC-II Recommendation 4.1.

In countries with multiple racial or ethnic groups, it is not uncommon that contributors to a mixed stain or a DNA mixture belong to different ethnic origins. This paper derives a general formula for evaluating the likelihood ratio in such situations based on the commonly adopted Recommendation 4.1 of the U.S. Second National Research Council Report on the evaluation of DNA evidence. The restrictive Hardy-Weinberg assumption is not taken in this paper. Our formula generalizes the results of Fung and Hu for a single ethnic group, and of Weir et al. under the Hardy-Weinberg law for a single, and Fukshansky and Bär for multiple ethnic groups. The effect of different ethnic groups of contributors to the interpretation of mixtures is illustrated through the analysis of the Simpson case.

Alleles↗
PubMed2002

Interpreting DNA mixtures with the presence of relatives.

The assessment of DNA mixtures with the presence of relatives is discussed in this paper. The kinship coefficients are incorporated into the evaluation of the likelihood ratio and we first derive a unified expression of joint genotypic probabilities. A general formula and seven types of detailed expressions for calculating likelihood ratios are then developed for the case that a relative of the tested suspect is an unknown contributor to the mixed stain. These results can also be applied to the case of a non-tested suspect with one tested relative. Moreover, the formula for calculating the likelihood ratio when there are two related unknown contributors is given. Data for a real situation are given for illustration, and the effect of kinship on the likelihood ratio is shown therein. Some interesting findings are obtained.

Algorithms↗
PubMed2002

Power of exclusion revisited: probability of excluding relatives of the true father from paternity.

In parentage testing using DNA markers, the formulae for calculating the probability of exclusion generally overstate the power of a test battery by considering its ability to exclude a random man. It is known that in many cases, in particular immigration applications, the false father is more likely to be a relative, e.g. brother, of the true father than an unrelated man. This work presents formulae that take this consideration into account. A practical example using Hong Kong data is provided to illustrate the effect of the modification. Also discussed is how the expected efficacy of a test battery will be affected when possible mutations and null alleles or genetic inconsistencies are taken into consideration.

DNA Fingerprinting↗
PubMed2002

The statistical evaluation of DNA mixtures with contributors from different ethnic groups.

The effect of a structured population on the evaluation of forensic mixed stains has been considered by the authors and others. However, in countries with multiple racial or ethnic groups, it is not uncommon that contributors to a DNA mixture are of different ethnic groups. A famous example is the OJ Simpson case in which the suspect was an African-American, the victims were Caucasian Americans and the true perpetrator(s) could be from any ethnic group(s). In this paper six common mixture cases are considered and the formulae for likelihood ratios are derived. These formulae can help forensic DNA scientists acquire a better understanding of the problem. The effect of different ethnic groups is illustrated using a case in Hong Kong.

Alleles↗