John Bacon-Shone

A new graphical method for detecting single and multiple outliers in univariate and multivariate data

SUMMARY A new graphical approach based on Wilkss (1963) statistic is proposed. The method is found to be useful in the detection of outliers in univariate and multivariate data. Masking and swamping effects in the sample are easily revealed. The method is illustrated with examples and simulations.

Bayesian Risk Ratio Analysis

Abstract The classical confidence interval approach has failed to find exact intervals, or even a consensus on the best approximate intervals, for the ratio of two binomial probabilities, the so-called risk ratio. The problem is reexamined from a Bayesian viewpoint, and a simple graphical presentation of the risk ratio assessment is given in such a way that sensitivity to the selected prior distribution can be readily examined.

The prevalence and correlates of severe social withdrawal (hikikomori) in Hong Kong: A cross-sectional telephone-based survey study

Background: Severe social withdrawal behaviors among young people have been a subject of public and clinical concerns. Aims: This study aimed to explore the prevalence of social withdrawal behaviors among young people aged 12–29 years in Hong Kong. Methods: A cross-sectional telephone-based survey was conducted with 1,010 young individuals. Social withdrawal behaviors were measured with the proposed research diagnostic criteria for hikikomori and were categorized according to the (a) international proposed duration criterion (more than 6 months), (b) local proposed criterion (less than 6 months) and (c) with withdrawal behaviors but self-perceived as non-problematic. The correlates of social withdrawal among the three groups were examined using multinomial and ordinal logistic regression analyses. Results: The prevalence rates of more than 6 months, less than 6 months and self-perceived non-problematic social withdrawal were 1.9%, 2.5% and 2.6%, respectively. In terms of the correlates, the internationally and locally defined socially withdrawn youths are similar, while the self-perceived non-problematic group is comparable to the comparison group. Conclusions: The study finds that the prevalence of severe social withdrawal in Hong Kong is comparable to that in Japan. Both groups with withdrawal behaviors for more or less than 6 months share similar characteristics and are related to other contemporary youth issues, for example, compensated dating and self-injury behavior. The self-perceived non-problematic group appears to be a distinct group and the withdrawal behaviors of its members may be discretionary.

Factors influencing indoor air quality in Hong Kong: Measurements in offices and shops

Abstract Comparisons of levels of respirable suspended particulates, carbon monoxide, carbon dioxide, nitrogen dioxide, volatile organic compounds and nicotine have been made between indoor and outdoor air in 35 street‐level shops and 35 offices in Hong Kong. Additionally, counts of bacteria and fungi were made indoors. In shops, the study showed that the air quality was principally determined by outdoor air, with highly significant correlations between indoor and outdoor levels of RSP, CO and NO2. The levels of these substances were significantly lower in offices. Measurement of analytes related to tobacco smoking showed extremely low levels of environmental tobacco smoke in both shops and offices, but the overall numbers of smokers in such establishments was small. For offices, occupier complaints regarding drowsiness, headache and symptoms of eye, nose and respiratory tract irritation were positively associated with CO2 levels. NO2, CO, toluene and benzene levels did not show any relationship to occupi...

A comparison of expiratory flow rates in two breathing circuits used for manual inflation of the lungs

Summary Manual inflation of the lungs by the ‘bag squeezing method’ (bagging) is commonly used by physiotherapists in the management of intubated patients. A wide variety of ‘bagging’ circuits are available and the peak expiratory flow rate that can be achieved is influenced by the circuit components. A high expiratory flow rate is desirable as it is believed to be one of the factors that determines the effectiveness of secretion mobilisation during a simulated cough in intubated patients. This study was designed to compare the expiratory flow rates resulting from the elastic recoil of a test-lung using the Mapleson-C breathing system and the Laerdal self-inflating resuscitator. Our data demonstrated that for any given pressure gradient the measured peak expiratory flow was higher with the Laerdal self-inflating resuscitator (p

Situational versus pervasive hyperactivity in a community sample

Groups of home and school situational hyperactive primary schoolboys identified from the community were compared with pervasive hyperactive and non-hyperactive controls on a wide range of measures. The hyperactive groups tended to persist in the same category over a half-year period. Both situational hyperactive groups had lower measured activity levels than the pervasive hyperactive group and only the latter differed from non-hyperactive controls. Home hyperactivity was characterized by poor family relationships and was not distinguishable from non-hyperactive home-antisocial controls. School hyperactive boys had specific correlates of low intelligence, motor clumsiness, poor reading and academic abilities. Pervasive hyperactive subjects differed from both situational groups in showing a higher percentage of delayed language development. While home hyperactivity has dubious identity, the distinct pattern of external correlates in school and pervasive hyperactivity speak for the need to regard these as separate entities.

Screening for congenital hypothyroidism in Hong Kong

A pilot cord blood TSH screening program for congenital hypothyroidism was commenced in Hong Kong in April 1982. By April 1984, 14 411 neonates born in two hospitals were screened for this disorder. Five cases of primary hypothyroidism and two cases of transient hypothyroidism were detected. The detection of cases of congenital hypothyroidism with only moderately elevated cord blood TSH values means that the recall rate will remain high.

A Comparison Between Two Models for Predicting Ordering Probabilities in Multiple-Entry Competitions

To predict ordering probabilities of a multiple-entry competition (e.g. a horse-race), two models have been proposed. Harville proposed a simple and convenient model that can easily be used in practice. Henery proposed a more sophisticated model but it has no closed form solution. In this paper, we empirically compare the two models by using a series of logit models applied to horse-racing data. In horse-racing, many previous studies claimed that the win bet fraction is a reasonable estimate of the winning probability. To consider complicated bet types which involve more than one position, ordering probabilities (e.g. P(horse i wins and horsej finishes 2nd)) are required. The Harville and Henery models assume different running time distributions and produce different sets of ordering probabilities. This paper illustrates that the Harville model is not always as good as the Henery model in predicting ordering probabilities. The theoretical result concludes that, if the running time of every horse is normally distributed, the probabilities produced by the Harville model have a systematic bias for the strongest and weakest horses. We concentrate on the horse-racing case but the methodology can be applied to other multiple-entry competitions.

Peak oxygen uptake of 12-18-year-old boys living in a densely populated urban environment

The purposes of this study were to provide data on the peak VO2 of 12-18-year-old boys from Hong Kong, a densely populated urban environment; to compare these data with those for other similarly aged populations; and to examine the correlations between peak VO2 and various anthropometric parameters of this group. A stratified, random sample of 86 ethnic Chinese boys had their peak VO2 determined using an on-line gas analysis system during incremental, treadmill running. The mean peak VO2 of the boys was 2.7 SD 0.44 l.min-1 or, when expressed in relation to body mass, 52.0 SD 5.8 ml.kg-1.min-1. Peak VO2 (l.min-1) was significantly correlated with body mass (r = 0.72, p < 0.001, age (r = 0.49, p < 0.001) and height (r = 0.71, p = 0.001). Peak VO2 (ml.kg-1.min-1) showed no correlation with age or height. These data suggest that this population group has peak VO2 values very similar to those observed in boys from most other population groups.

Ranking methods for compositional data

In the analysis of compositional data, zero components or a non‐normal distribution of the log‐ratios severely limits the analysis that can be done. Ranking across both cases and components, before scaling, is suggested as a possible new approach. The idea is illustrated with a data set which compares the results with other methods including replacement of Os by small positive quantities and other ranking methods.