Statistical modelling by neural networks

In this thesis the two disciplines of Statistics and Artificial Neural Networks are combined into an integrated study of a data set of a weather modification Experiment. An extensive literature study on artificial neural network methodology has revealed the strongly interdisciplinary nature of the research and the applications in this field. An artificial neural networks are becoming increasingly popular with data analysts, statisticians are becoming more involved in the field. A recursive algoritlun is developed to optimize the number of hidden nodes in a feedforward artificial neural network to demonstrate how existing statistical techniques such as nonlinear regression and the likelihood-ratio test can be applied in innovative ways to develop and refine neural network methodology. This pruning algorithm is an original contribution to the field of artificial neural network methodology that simplifies the process of architecture selection, thereby reducing the number of training sessions that is needed to find a model that fits the data adequately. [n addition, a statistical model to classify weather modification data is developed using both a feedforward multilayer perceptron artificial neural network and a discriminant analysis. The two models are compared and the effectiveness of applying an artificial neural network model to a relatively small data set assessed. The formulation of the problem, the approach that has been followed to solve it and the novel modelling application all combine to make an original contribution to the interdisciplinary fields of Statistics and Artificial Neural Networks as well as to the discipline of meteorology.Mathematical SciencesD. Phil. (Statistics

Exploring the influence of instant messaging and video conferencing on the quality of project communication

Growth in computer-mediated communication (CMC) technologies such as instant messaging (IM) and video conferencing (VC) has led to a need to explore the utilisation and influence of these tools on the quality of project communication, which must still be established. This article reports the results of a survey conducted among 210 project practitioners using CMC in various industries to determine how, why and what each medium is used for, and how these media influence factors that promote quality communication. Some results showed that the use of both instant messaging and video conferencing in projects is moderate and both improve the quality of communication in virtual teams, however in different ways

Predicting a dissociative disorder from type of childhood maltreatment and abuser-abused relational tie

We investigate the types of childhood maltreatment and abu-ser–abused relational ties that best predict a dissociative disorder (DD). Psychiatric inpatients (n = 116; mean age = 35; F: M = 1.28:1) completed measures of dissociation and trauma. Abuse type and abuser–abused relational ties were recorded in the Traumatic Experiences Questionnaire. Multidisciplinary team clinical diagnosis or administration of the SCID-D-R to high dissociators confirmed DD diagnoses. Logit models described the relationships between abuser–abused relational tie and the diagnostic grouping of patients, DD present (n = 16) or DD absent (n = 100). Fisher’s exact tests measured the relative contribution of specific abuse types. There was a positive relationship between abuse frequency and the pre-sence of DD. DD patients experienced more abuse than patients without DDs. Two combinations of abuse type and relational tie predicted a DD: childhood emotional neglect by biological parents/siblings and later emotional abuse by inti-mate partners. These findings support the early childhood etiology of DDs and subsequent maladaptive cycles of adult abuse. Enquiries about childhood maltreatment should include a history of emotional neglect by biological parents/siblings. Adult emotional abuse by intimate partners should assist in screening for DDs.The South African National Research Foundation and the Department of Psychiatry and Faculty of Health Sciences of the University of Pretoria.http://www.tandfonline.com/loi/wjtd202018-02-23PsychiatryStatistic

HIV sero-positivity in recently admitted and long-term psychiatric in-patients : prevalence and diagnostic profile

OBJECTIVE: Research on HIV in South Africa has not reflected the impact of the disease on psychiatric patients. The aims of the study were: to compare the HIV prevalence among patient groups in Weskoppies Hospital; to compare psychiatric diagnoses of infected and non-infected patients; to assess intravenous drug use and high-risk sexual behaviour; to establish HIV-syphilis association; and to investigate the rapid test performance for screening, compared to the confirmatory ELISA test. METHOD: Onehundred- and-ninety-five patients were grouped into four categories according to their duration of admission and gender. HIV rapid testing, HIV ELISA, syphilis-RPR and TPHA testing were performed. RESULTS: The HIV prevalence of 11% in the sample was significantly associated with ‘gender-and-duration-of-admission’ categories (p=0.003). No significant association between HIV infection and psychiatric diagnoses or intravenous drug use was found, but a significant association existed between HIV infection and high-risk sexual behaviour (p=0.002), and between HIV and syphilis (p=0.012). The HIV rapid screening test had a sensitivity of 91.7% and a specificity of 98.2%. CONCLUSION: The overall HIV prevalence at Weskoppies Hospital remains lower than the national average, but has increased since a previous local study. The rapid test for HIV had a lower sensitivity than was expected, and it is recommended that HIV ELISA testing be performed as a first line test in the setting of hospitalised patients. Due to the high prevalence of HIV and syphilis in the psychiatric population it is recommended that all patients be tested for both of these diseases.This study was financially supported by a grant from the Research Committee of the Faculty of Health Sciences, University of Pretoria.http://www.journals.co.za/ej/ejour_medjda.htm

Dissociative mental states are canonically associated with decreased temporal theta activity on spectral analysis of EEG

Quantitative electroencephalographic (QEEG) changes relating to dissociative experiences have only rarely been demonstrated and dissociative states were not quantified in those studies. The aim of this study was to explore concurrent associations between quantified dissociative states and QEEG spectral parameters, in particular theta activity, in psychiatric patients. Fifty psychiatric patients completed the State Scale of Dissociation (SSD) immediately after a 15-minute EEG recording. The EEG was assessed by conventional clinical visual analysis, as well as by quantitative (QEEG) spectral analysis. Canonical analysis was performed between the set of SSD subscale scores and these QEEG parameters: alpha-theta magnitude ratios, and relative as well as absolute theta magnitude obtained from right and left mid- to posterior-temporal and parieto-occipital derivations. The SSD transferred well to the present data in terms of reliability and internal-criterion-related validity. The SSD and DES correlated significantly (r=0.73;p<0.001). Conventional EEG analysis identified 29 EEGs (58%) as abnormal. The main abnormality in 23 EEGs was slowing, maximal temporally in half of these cases. Canonical analyses confirmed a statistically significant relationship between the dissociation variables (especially conversion and depersonalization symptoms) and the QEEG variables (especially relative theta magnitude in the temporal regions) (R=0.72; p=0.03 for SSD-QEEG and R=0.66; p=0.04 for DES-QEEG). Quantified dissociative mental states are positively canonically associated with decreased temporal theta activity and increased alpha-theta ratios on QEEG in psychiatric patients with a high tendency to dissociate. The potential implications of the dissociation theta-alpha relationship for understanding normal attentional processes need to be studied further.This article refers to: Krüger, C. (1998). The State Scale of Dissociation: Development, psychometric validation, and application in a study of concurrent electro-encephalographic correlates . Unpublished MD thesis, University of Warwick, United Kingdom. Available at http://wrap.warwick.ac.uk/38291/The Research Committee of the Faculty of Health Sciences, University of Pretoria for the research assistant post, and from the Research Development Programme of the University of Pretoria.http://www.tandfonline.com/loi/wjtd20hb2013ay201

A survey of HIV-related knowledge among adult psychiatric patients. A South African Study - Part 2

OBJECTIVE: Studies have reported an increased prevalence of HIV infection among psychiatric patients. Inaccurate HIV knowledge is included as a factor in the increased risk of HIV infection in the mentally ill, but few studies have looked specifically at this factor. The aims of the study were to determine the knowledge of HIV and its transmission among adult psychiatric patients at Weskoppies Hospital and to determine the relationship between HIV knowledge and HIV risk behaviour. METHOD: Structured interviews were conducted with 113 consenting adult patients at Weskoppies Hospital. They were divided into three groups according to their length of hospital stay. The structured interview included questions about demographic data, the diagnoses and the AIDS Risk Behaviour Knowledge Test (AIDS-KT). Scores of 13 out of 13 represented accurate knowledge of HIV (level I); scores of 10-12 represented good knowledge (level II); scores of ≤9 represented poor knowledge (level III). RESULTS: A total of 104 patients (92%) demonstrated excellent knowledge of HIV and its transmission (levels I and II). There was no significant linear association between HIV knowledge and risk-behaviour scores (Pearson’s correlation coefficient r=-0.11). CONCLUSION: The presence of high-risk behaviours despite good HIV-related knowledge in this group of patients, leads us to think that knowledge alone will not limit HIV risk behaviours. For this reason, educational programmes should not be limited to interventions that simply increase knowledge about HIV infection but should extend to clinical factors, including patients’ motivation and readiness to change their behaviour.http://www.journals.co.za/ej/ejour_medjda.htm

Assessment of the value of group-based counselling for career construction

This article reports on the change in the career adaptability of participants exposed to an intervention programme characterized by career and selfconstruction principles compared to the change in participants who participated in standard, traditional career counselling lessons. Convenience and purposive sampling were used to select two groups (experimental and comparison of Grade 11 learners). Intervention occurred in both experimental groups. A mixed methods, quasi-experimental, pre-test/posttest comparison group design was used to gather data. Pre- and post-test scores obtained on the Career Adapt-Abilities Scale (CAAS) were analysed. The quantitative results suggested that the intervention programme did not improve participants’ career adaptability compared to standard, traditional career counselling lessons as measured by the CAAS. Future research should include the use of measures of self-reflection and meaning-making to test the direct effects of experimental interventions.https://www.tandfonline.com/loi/rady20am2019Educational PsychologyStatistic

Exploring the influence of instant messaging and video conferencing on the quality of project communication

Growth in computer-mediated communication (CMC) technologies such as instant messaging (IM) and video conferencing (VC) has led to a need to explore the utilisation and influence of these tools on the quality of project communication, which must still be established. This article reports the results of a survey conducted among 210 project practitioners using CMC in various industries to determine how, why and what each medium is used for, and how these media influence factors that promote quality communication. Some results showed that the use of both instant messaging and video conferencing in projects is moderate and both improve the quality of communication in virtual teams, however in different ways.Die groei in rekenaar-bemiddelde kommunikasietegnologie soos kitsboodskappe en videokonferensies het gelei tot ʼn behoefte om die benutting en invloed van hierdie tegnologie op die gehalte van projekkommunikasie te verstaan aangesien dit nog nie vasgestel is nie. Hierdie artikel rapporteer die resultate van ‘n opname wat gedoen was onder 210 projekpraktisyns wat CMC’s gebruik in verskeie industrieë om te bepaal hoe, hoekom en waarvoor elke medium gebruik word, en hoe hierdie media die faktore beïnvloed wat kwaliteitkommunikasie bevorder. Sommige resultate toon dat die gebruik van beide hierdie tipe media in projekte matig is en dat kitsboodskappe en videokonferensies albei die gehalte van kommunikasie in virtuele spanne verbeter maar egter op verskillende maniere.http://reference.sabinet.co.za/sa_epublication/structam2016Graduate School of Technology Management (GSTM)Statistic

A survey of risk behaviour for contracting HIV among adult psychiatric patients. A South African study - Part 1

OBJECTIVE: Various studies have reported increased prevalence of HIV infection among psychiatric patients. Psychiatric patients are under-evaluated in terms of their HIV risk behaviour. The study sought to establish the prevalence of HIV risk behaviour and determine the association between risk behaviour and demographic and clinical variables. METHOD: Participants were 113 consenting adult in-patients. A structured interview was conducted with each participant. A total risk behaviour score was calculated. From the risk score, three risk behaviour categories were identified: 0 = no risk; 1 to 3 = medium risk; 4 to 9 = high risk. Associations between HIV risk behaviour and demographic and clinical variables were analysed. RESULTS: Of the 113 participants, 68% were men and 32% women. The mean age was 38. Forty-five per cent were sexually active and 48% fell into the “no-risk group”, 29% in the “medium-risk” group, and 23% in the “high-risk” group. Female patients with a history of treatment for sexually transmitted disease and a diagnosis of personality disorder were associated with being sexually abused. Having multiple sex partners was associated with diagnoses of substance-related disorders and cognitive disorders. Sex with someone known for less than 24 hours was associated with long-term hospitalisation and diagnoses of cognitive and personality disorders. CONCLUSION: The study confirmed that mentally ill patients are vulnerable and may be victimised. The study also suggests that mental illness may impair appreciation of consequences and lead to high-risk behaviour for contracting HIV. Special care should be taken to protect female patients in psychiatric institutions.http://www.journals.co.za/ej/ejour_medjda.htm

Physical activity of children from a small rural town, South Africa

INTRODUCTION : Physical activity plays an integral role in the normal physical, mental, social and cognitive development of children. One of the main reasons for overweight children in low- and middle-income countries like South Africa is inactivity. This study’s aim was to describe the physical activity measured in boys and girls from section 21, quintile 5 pre-primary and primary schools in a small rural South African town and to compare it with recommended international physical activity levels. METHOD : Seventy-eight rural children, representing Caucasian and black African children, divided into three age groups, were issued a piezoelectric pedometer for seven complete days. Pedometer data obtained were total steps, aerobic steps, aerobic walking time, calories and distance. Steps per day were compared with international levels. Correlation statistics examined the association between physical activity and adiposity. RESULTS : Boys in the age groups 9–11 and 12–14 years are statistically more active than girls of the same age (p = 0.005 and 0.045 respectively). Although girls’ physical activity levels tend to decrease with age, their aerobic activity levels increase with age. This group of rural children’s physical activity levels are far lower than the recommended international normative levels. No correlation was found between physical activity and adiposity. CONCLUSION : The pedometer data indicated that gender and age influence the activity of children. This group of rural children’s physical activity is far less than international normative levels. Nine to 11-year-old boys are the most active boys, and girls of 12–14 years old are the most aerobic active girls in this study, therefore the authors concluded that, to increase physical activity, the age group 9–11 may be the ideal age to focus on for gender-specific intervention programmes.http://www.safpj.co.za/index.php/safpjhttp://www.tandfonline.com/oemdam2016Sports MedicineStatistic