Bivariate transition model for analysing ordinal and nominal categorical responses: an application to the Labour Force Survey data

In many panel studies, bivariate ordinal–nominal responses are measured and the aim is to investigate the effects of explanatory variables on these responses. A regression analysis for these types of data must allow for the correlation among responses of the same individual. To analyse such ordinal–nominal responses using a proper weighting approach, an ordinal–nominal bivariate transition model is proposed and maximum likelihood is used to find the parameter estimates. We propose a method in which the likelihood function can be partitioned to make possible the use of existing software. The approach is applied to the Labour Force Survey data in Iran, where the ordinal response, at the first period, is the duration of unemployment for unemployed people and the nominal response, in the second period, is economic activity status of these individuals. The interest is to find the reasons for staying unemployed or moving to another status of economic activity.     

Missing data mechanisms and their implications on the analysis of categorical data

We review some issues related to the implications of different missing data mechanisms on statistical inference for contingency tables and consider simulation studies to compare the results obtained under such models to those where the units with missing data are disregarded. We confirm that although, in general, analyses under the correct missing at random and missing completely at random models are more efficient even for small sample sizes, there are exceptions where they may not improve the results obtained by ignoring the partially classified data. We show that under the missing not at random (MNAR) model, estimates on the boundary of the parameter space as well as lack of identifiability of the parameters of saturated models may be associated with undesirable asymptotic properties of maximum likelihood estimators and likelihood ratio tests; even in standard cases the bias of the estimators may be low only for very large samples. We also show that the probability of a boundary solution obtained under the correct MNAR model may be large even for large samples and that, consequently, we may not always conclude that a MNAR model is misspecified because the estimate is on the boundary of the parameter space.     

Diagnosing physical abuse using Bayes' Theorem: a preliminary study

Objectives. To perform a preliminary study to compare the patterns of bruises in a physically abused group of children and a control group; to investigate whether these could be modelled statistically to enable probabilities of typical bruise patterns to be calculated; to apply Bayes' Theorem to find the probability that a child with a given bruise pattern has been the subject of physical abuse. Design. An observational study. Setting. Cardiff and Vale of Glamorgan. Subjects. Children who have suffered child physical abuse, 0–14 years. The diagnosis was confirmed at a case conference in all cases. A control group of 289 children who presented to the Accident and Emergency Department at the Cardiff Royal Infirmary after an accidental injury. Main outcome measures. The distribution bruise pattern in three regions of the body. The posterior probability of abuse for a given bruise pattern. Results. The bruise distribution in physically abused and control children was well described by a negative binomial distribution. There was a different distribution for the three different regions of the body in physically abused children. The bruising frequency and distribution for the physically abused group was very different from that of the controls. We were able to use parameters derived from these distributions to calculate posterior probabilities of physical abuse given a particular pattern of bruises using Bayes' Theorem. Conclusions. This preliminary study demonstrates that we can use Bayes' Theorem to combine prior probabilities of physical abuse with observed patterns of bruising in given children to obtain posterior probabilities of abuse. This principle has considerable potential for better diagnosis of the physically abused child. © 1998 John Wiley & Sons, Ltd.     

Toward a carnivalesque analysis of hacking: A qualitative study of Iranian hackers

This study sought to analyze Iranian hackers’ lived experiences based on the concept of the carnival of crime in cultural criminology. Fifty-four in-depth semi-structured interviews were conducted with young hackers. Moreover, their behaviors were observed along with those of other hackers. The data were coded through a thematic analysis using MAXQDA software. The study's findings indicated that cyberspace had created a carnivalesque utopia that allowed the young Iranian hackers to experience the pleasure of crime. By trespassing the rational frameworks of the modern world and altering the trends of knowledge creation as a means for subjugation, Iranian hackers contribute to the meaning-construction policies of those in power and challenge authoritarian aesthetics by invading their electronic domain. It was also found that the carnivalesque lives of hackers provided them with a variety of opportunities for disrupting the rhythms of production and creating an underground carnivalesque economy based on their level of knowledge.     

Behavioural problems of adolescents in secure residential youth care: Gender differences and risk factors

Adolescents in secure residential care mostly suffer from serious behavioural problems, often accompanied by trauma and adverse family circumstances. This paper presents findings of a comparison of behavioural problems and risk factors of 255 boys and girls (aged 12 to 18 years) in secure residential care in the Netherlands and their association with behavioural problems. A cross-sectional design and standardized questionnaires were used to measure behavioural problems and individual and familial risk factors. By using independent-sample t tests, the severity of these factors in boys and girls was compared, and by using structural equation modelling (SEM), associations between these factors and behavioural problems were investigated. The findings of the study show that post-traumatic stress disorder (PTSD) symptoms, maladaptive emotion regulation, impaired perceived competence and internalizing behavioural problems were more severe in girls than in boys. Boys experienced more severe externalizing behavioural problems and more family problems than girls. Maladaptive emotion regulation, PTSD symptoms, perceived competence and parenting problems were related to behavioural problems. The results indicate that treatment for girls should address PTSD symptoms, perceived competence and maladaptive emotion regulation and that extra attention for family problems in the treatment of boys is warranted.     

SCHEDULING HYBRID FLOWSHOPS IN PRINTED CIRCUIT BOARD ASSEMBLY LINES*

We treat a three‐stage hybrid flowshop for the production of printed circuit boards (PCB), suggested to us by a real‐life production situation. The problem is to determine a schedule that minimizes the makespan for a given demand profile over a finite planning horizon. We propose a global procedure that utilizes genetic algorithms and three subproblems. The performance of the procedure is evaluated via experimentation over thousands of problem realizations that are randomly generated. The experimental results show the efficiency of the global procedure and provides qualitative answers to the allocation of machines to the various stages.     

Early social referencing predicts object mastery motivation in infancy: Social antecedents of object mastery motivation

The researchers sought to understand the typical development of social referencing and object mastery motivation in infancy and to determine the relationship between social referencing and object mastery behaviors in infants from 7 to 22 months of age. The study included 36 infants who were followed as part of a longitudinal study of at-risk infants but were not determined to need care in the neonatal intesive care unit at birth. Both mastery behaviors of persistence and success showed a statistically significant effect of age, while social behaviors remained stable from 7 to 22 months. Social behaviors at 7 and 10 months were correlated with persistence at 22 months and success at 16 to 22 months demonstrating that early social referencing predicts object mastery behaviors in later infancy. Further research should determine if this trend extends to early childhood.