Orientador: Antonio Roberto Balbo / Banca: Márcia Marcondes Altimari Samed / Banca: Edmea Cassia Baptista / Resumo: Este trabalho visa a investigação e implementação de métodos Primal - Dual Previsor-Corretor de Pontos Interiores com a estratégia de busca unidimensional, e a aplicação destes em problemas de Despacho Econômico e Ambiental. Objetiva-se utilizar estes métodos para determinar soluções aproximadas e consistentes dos problemas causados citados, que forneçam a solução de minimização dos custos dos combustíveis empregados na geração termoelétrica de energia, otimizando um processo de alocação da demanda de energia elétrica entre as unidades geradoras disponíveis, de tal forma que as restrições operacionais sejam atendidas e que o custo de geração é minimizado. Pretende-se também, analisar o problema de Despacho Ambiental com um objetivo único quando se acopla a este o Problema de Despacho Econômico e busca-se, simultaneamente, a minimização dos custos de geração e a redução da emissão de poluentes na natureza. Os métodos foram implementados, testados em Problemas de Despacho Econômico e Ambiental, e o seu desempenho foi comparado com outros métodos já utilizados, cujos resultados são encontrados na literatura / Abstract: This work aims the investigation and implementation of Primal-Dual Predictor-Corrector interior points methods, with the strategy of one-dimensional search, and its application in Economic and Environmental Dispatch Problems. It pretends to use these methods to determine approximate and consistent solutions of the mentioned problems, that provide the solution to minimize the fuel costs used in thermoelectric power generation, optimizing an allocations process of eletric power demand among available generation units, such that the operational constraints are attended and that generation cost is minimized. It too pretends to analyze the Environmental Dispatch Problem with the one objective when it is joined with the Dispatch Problems and it searchs, simultaneously, the minimization of the generation costs and the reduction of emission of the polluants in the nature. The methods were implemented, tested on the Economic and Environemental Dispatch Problems and its performance was compared with others method currently used, whose results are found in the literature / Mestre

Este trabalho descreve o desenvolvimento de um sistema de controle com compensação de tempo morto aplicado a um ventilador para simular os efeitos do vento em modelos de embarcações. O sistema é instalado no tanque de provas do Departamento de Engenharia Naval da Escola Politécnica da USP. Um sistema de controle baseado em computador é elaborado para a realização dos testes e validação, procedendo-se inicialmente a identificação do sistema a ser controlado. Na malha de controle, o sinal de referência é a velocidade do vento desejada em uma distância pré-definida do ventilador e pode ser tanto um valor constante (representando um vento constante) ou um valor variante no tempo (representando uma rajada de vento). O sistema atuador consiste de um inversor de frequência que aciona o ventilador e a velocidade do vento é medida por um anemômetro, cujo sinal é usado como realimentação para o controlador. A sintonia da malha é realizada pelo método do modelo interno (IMC) e o efeito do tempo morto é observado nos testes, aplicando-se o compensador baseado no Preditor de Smith para minimizá-lo. Pelos resultados dos ensaios, conclui-se que o Preditor de Smith melhora o desempenho do sistema de geração de vento. / This paper describes the development of a control system with dead time compensation applied to a fan to simulate wind effects in models of vessels. The system is installed on the academic towing tank of the Naval Architecture and Oceanic Engineering Department of the University of São Paulo. A control system based on computer is designed for testing and validation, proceeding initially to identify the system to be controlled. In the control loop, the set-point is the desired speed of the wind on a pre-defined distance from the fan and it can be either a constant value (representing a constant wind) or a time-varying value (representing a wind gust). The actuator system consists of a frequency-inverter that drives the fan and the wind speed is measured by an anemometer, whose signal is used as feedback to the controller. The tuning of the controller is made by the internal model control (IMC) and the effect of dead time is observed in the tests, applying the compensator based on Smith Predictor to minimize it. Through the results from the tests, it was concluded that the Smith Predictor improves the performance of the wind generation system.

INTRODUÇÃO: O Lúpus Eritematoso Sistêmico (LES) é uma doença inflamatória crônica que pode acometer qualquer órgão ou sistema. O acometimento do coração pode ocorrer em até 50% dos casos e não existem estudos de prevalência de eventos arrítmicos (EA) em pacientes com LES, nem de correlações laboratoriais preditoras de sua ocorrência. OBJETIVOS: Estabelecer a taxa de ocorrência de EA e identificar variáveis laboratoriais preditoras de sua ocorrência em pacientes com LES em seguimento em ambulatório de hospital terciário; estabelecer a associação entre o uso de cloroquina com a ocorrência de EA e óbitos (tipo, número e tempo de seguimento). MÉTODOS: Foi realizado um estudo clínico descritivo, observacional e aberto com pacientes em seguimento ambulatorial no Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo que foram submetidos a avaliação clínica, exames laboratoriais, ECG de repouso e Holter de 24h. A associação entre as variáveis e os EA foi avaliada por meio dos testes qui-quadrado, razão de verossimilhança, teste exato de Fisher, teste t-Student, teste não-paramétrico de Mann-Whitney, regressão logística múltipla e curva ROC. RESULTADOS: Entre agosto/2005 e agosto/2006 foram estudados 325 pacientes consecutivos, sendo 8 excluídos. A idade média foi de 40,25 anos, 91% mulheres. O tempo médio do diagnóstico de LES foi de 11,36 anos e apenas 6 pacientes apresentaram critérios para atividade do LES (escore SLEDAI). Duzentos e vinte e um pacientes estavam em uso de cloroquina. Alterações ao ECG ocorreram em 66 pacientes (20,82%): 5 bloqueios atrioventriculares de 1º grau; 4 bradicardias sinusais; 4 taquicardias sinusais e 1 supraventricular; 6 bloqueios do ramo direito (BRD); 2 bloqueios do ramo esquerdo (BRE); 45 QT prolongados. Ao Holter foram identificados 4 pacientes com pausas > 2,0 segundos; 45 com FC mínima < 50bpm; 90 com extrassístoles supraventriculares (ESV); 26 com taquiarritmias supraventriculares (FA/TA); 65 com extrassístoles ventriculares (EV). Foram registrados 7 óbitos (2,47%). Idade acima de 40 anos foi preditora da ocorrência de EA (p=0,002; OR=2,523; IC 95%= 1,389-5,583). A presença do anticorpo anticardiolipina foi preditora da ocorrência de BRD/BRE (p = 0,005; OR 3,989; IC 95% = 1,615-9,852). Títulos de C3 abaixo de 105mg% foram preditores de menor probabilidade de ocorrência de FC mínima < 50bpm (p=0,016; OR=1,018; IC 95%=1,003-1,033). Os preditores para a ocorrência de EV foram a idade (p=0,002; OR=1,051; IC95%=1,018-1,085) e a duração do QRS (p=0,005; OR=1,061; IC95%=1,018-1,106); quanto mais avançada a idade e quanto mais largo o QRS, maior a probabilidade de ocorrência de EV. Para a ocorrência de TA/FA, os preditores foram a idade (p<0,001; OR=1,100; IC95%=1,050-1,154) e o tempo de uso cloroquina (p=0,035; OR=0,921; IC95%=0,853-0,994); quanto mais avançada a idade e quanto menor o tempo de uso de cloroquina, maior a probabilidade de ocorrência de TA/FA. Pacientes com mais de 50 anos e tempo de uso de cloroquina inferior a 8 anos tiveram mais TA/FA. CONCLUSÕES: Neste estudo, que avaliou pacientes com LES em seguimento ambulatorial em hospital terciário, a taxa de ocorrência de EA foi elevada; a sua correlação com variáveis laboratoriais identificou como preditores de maior ocorrência: idade acima de 40 anos, título de C3 abaixo de 105mg% e presença de anticorpo anticardiolipina. A cloroquina demonstrou efeito protetor cardíaco sobre a evolução da doença. / INTRODUCTION: Systemic Lupus Erythematosus (SLE) is a chronic inflammatory illness that can affect any organ and system. Up to 50% of patients have their heart affected and there are no prevalence studies of arrhythmic events (AE) in SLE patients and laboratory predictors are also unknown. OBJECTIVES: To establish the rate of occurrence of AE and to identify laboratory predictors in outpatients with SLE; to establish the association between chloroquine use and the occurrence of AE and death (type, number and time of follow-up). METHODS: A descriptive, observational and opened clinical study was carried out with SLE oupatients selected from the Rheumatology clinic of São Paulo University Medical School, Brazil. They were submitted to clinical evaluation, laboratory exams, resting-ECG and 24-hour Holter monitoring. Statistics: The association between the variables and the occurrence of AE was assessed by chi-square, likelihood ratio, Fishers test, t-Student, Mann-Whitney, ROC curve and logistic regressions. RESULTS: Between august/05-august/06, 325 consecutive patients were studied. Resting-ECG abnormalities were found in 66 patients, rate of 20.82%. The average age was 40.25yo, 91% female. The average time of SLE diagnosis was of 11.36y and only 6 presented criteria for diseases activity (SLEDAI score). There were 221 patients using chloroquine. ECG disturbances found: 5 1st degree AV-block; 4 sinus bradycardia; 4 sinus tachycardia and 1 supraventricular tachycardia; 6 RBBB; 2 LBBB; 45 long QT. At Holter monitoring: 4 pauses>2.0s; 45 HR<50bpm; 90 atrial ectopies; 26 atrial tachyarrhythmia; 65 ventricular ectopies. Seven death were registered (2.47%). Age above 40yo was predictor of AE (p=0.002; OR=2.5; 95%IC=1.4-5.6). Presence of anticardiolipine antibody was predictor of QRS>120ms occurrence (p = 0.005; OR 3.989; IC 95% = 1.615-9.852). C3 level bellow 105mg% was predictor of non-occurrence of HR<50bpm (p=0.02; OR=1.02;95% IC=1.003-1.03). The predictor for ventricular ectopies (VE) occurrence were age (p=0,002; OR=1,051; IC95%=1,018-1,085) and QRS duration (p=0,005; OR=1,061; IC95%=1,018-1,106); advanced age and longer QRS predicted greater probability of VE. For supraventricular tachyarrhythmia (AT/AF) the predictors were age (p<0,001; OR=1,100; IC95%=1,050-1,154) and time of Chloroquine use (p=0,035; OR=0,921; IC95%=0,853-0,994); advanced age and short time of Chloroquine use are related to greater probability of AT/AF. Patients older than 50y and using chloroquine for less than 8y had more AT/AF. CONCLUSIONS: The rate of AE occurrence was high (20%) and the correlation with laboratory variables identified predictors of occurrence of AE: age above 40 years, C3 level below 105mg% and anticardiolipin antibody. Chloroquine demonstrated cardiac protection effect.

Neste trabalho, os métodos de pontos interiores primal-dual e preditor corretor são estudados e desenvolvidos para o problema de minimização de custos na geração e perdas na transmissão do pré-despacho DC (fluxo de carga em corrente contínua) de um sistema de potência hidroelétrico, com base no modelo de fluxo em redes e no princípio do mínimo esforço. A estrutura matricial, resultante da simplificação do problema proposto pela inclusão do princípio do mínimo esforço, é estudada visando implementações eficientes. / In this work, the primal-dual and predictor corrector interior points methods are studied and developed for the predispatch DC problem that minimizes generation and transmission losses on hydroelectric power systems, on the basis of the network flow model and the minimum effort principle. The matrix structure, resulting of the simplification of the problem considered by inclusion of the minimum effort principle, is studied aiming efficient implementations. A disturbed primal-dual method is considered on the basis of a heuristic definition that determine the choice of the disturbance parameter. This method showed to be efficient in practice and converged in fewer iterations when compare with an existing implementation of the network flow model.

Com o crescimento urbano ao redor das minerações surgiram novos problemas como o desconforto dos vizinhos com vibrações, que podem provocar danos nas estruturas das casas, a poeira, os ultralançamento, a sobrepressão atmosférica, entre outros. Atualmente no Brasil as restrições ambientais são cada vez mais rígidas e são exigidos mais monitoramentos sismográficos como medida de controle ambiental. A Geosonic Inc. foi a primeira a usar o sistema de mapa de iso-velocidades, mas seu uso não é prática corrente no Brasil devido ao elevado custo de instrumentação e de operação no campo. Iramina (2002) desenvolveu um método com equações de carga-distância simulando um mapa de iso-velocidades. O objetivo deste trabalho é verificar a metodologia proposta por Iramina (2002), que construiu mapas de iso-velocidades usando oito monitoramentos unidirecionais para oito detonações diferentes e sequenciais numa mesma bancada e analisar alternativas para a construção dos mapas de iso-velocidade. Neste trabalho foram monitoradas quatro detonações e em cada uma delas, quatro direções diferentes foram selecionadas utilizando um total de 20 sismógrafos. As detonações avaliadas foram todas na mesma bancada e com características similares. Para cada direção foram estimados os parâmetros da equação carga-distância e foram construídos e comparados diferentes mapas de iso-velocidade. Conclui-se que a disposição dos geofones deve-se adequar aos objetivos do monitoramento. Oito a quinze geofones alinhados são adequados para uma curva carga-distância. Sessenta e quatro ou mais geofones, bem distribuídos espacialmente, podem gerar um mapa de iso-velocidades referente a uma única detonação. A alta variabilidade das características dos maciços rochosos parece não permitir bons resultados quando os sismógrafos não são bem distribuídos ao redor da detonação. / The urban growth around the open pit mines causes some problems hard to solve due to possible damage to structures built as result of unwanted ground vibration propagation, blast overpressure, flyrocks, water contamination and also particulate matter dispersion. Currently in Brazil, the environmental constraints are increasingly rigid and it is required seismographic monitoring as a measure of environmental control. Geosonic Inc. was the first to use the iso-seismic maps, but this technique is not commonly used in Brazil due to the high cost of instrumentation and field operation. Iramina (2002) developed a model of vibration predictor equations that simulates an iso-seismic map. Thus, the objective of this work is to verify the methodology developed by Iramina (2002), who implemented an iso-seismic map from eight unidirectional measurements in eight different and sequential detonations in the same bench and analyze alternatives for the construction of iso-seismic maps. Herein were monitored four detonations with four directions in each and 20 seismographs at most. All detonations were monitored in the same bench and with similar characteristics. For each direction were estimated the parameters of the vibration predictor equations and from these equations were obtained and compared different iso-seismic maps. Then, it is concluded that the arrangement of geophones should suit to the objectives of monitoring. In this sense, eight to fifteen aligned geophones are suitable for a good load-distance curve, sixty-four geophones or more spatially well distributed, must generate a iso-seismic map corresponding to a single detonation. The high variability of the characteristics of the rock mass does not seem to allow good results when the seismograph are not well distributed around the detonation.

One basic problem in statistical sciences is to understand the relationships among multivariate outcomes. Although it remains an important tool and is widely applicable, the regression analysis is limited by the basic setup that requires to identify one dimension of the outcomes as the primary measure of interest (the "dependent" variable) and other dimensions as supporting this variable (the "explanatory" variables). There are situations where this relationship is not of primary interest. For example, in actuarial sciences, one might be interested to see the dependence between annual claim numbers of a policyholder and its impact on the premium or the dependence between the claim amounts and the expenses related to them. In such cases the normality hypothesis fails, thus Pearson's correlation or concepts based on linearity are no longer the best ones to be used. Therefore, in order to quantify the dependence between non-normal outcomes one needs different statistical tools, such as, for example, the dependence concepts and the copulas. This thesis is devoted to modelling dependence with applications in actuarial sciences and is divided in two parts: the first one concerns dependence in frequency credibility models and the second one dependence between continuous outcomes. In each part of the thesis we resort to different tools, the stochastic orderings (which arise from the dependence concepts), and copulas, respectively. During the last decade of the 20th century, the world of insurance was confronted with important developments of the a posteriori tarification, especially in the field of credibility. This was dued to the easing of insurance markets in the European Union, which gave rise to an advanced segmentation. The first important contribution is due to Dionne & Vanasse (1989), who proposed a credibility model which integrates a priori and a posteriori information on an individual basis. These authors introduced a regression component in the Poisson counting model in order to use all available information in the estimation of accident frequency. The unexplained heterogeneity was then modeled by the introduction of a latent variable representing the influence of hidden policy characteristics. The vast majority of the papers appeared in the actuarial literature considered time-independent (or static) heterogeneous models. Noticeable exceptions include the pioneering papers by Gerber & Jones (1975), Sundt (1988) and Pinquet, Guillén & Bolancé (2001, 2003). The allowance for an unknown underlying random parameter that develops over time is justified since unobservable factors influencing the driving abilities are not constant. One might consider either shocks (induced by events like divorces or nervous breakdown, for instance) or continuous modifications (e.g. due to learning effect). In the first part we study the recently introduced models in the frequency credibility theory, which can be seen as models of time series for count data, adapted to actuarial problems. More precisely we will examine the kind of dependence induced among annual claim numbers by the introduction of random effects taking unexplained heterogeneity, when these random effects are static and time-dependent. We will also make precise the effect of reporting claims on the a posteriori distribution of the random effect. This will be done by establishing some stochastic monotonicity property of the a posteriori distribution with respect to the claims history. We end this part by considering different models for the random effects and computing the a posteriori corrections of the premiums on basis of a real data set from a Spanish insurance company. Whereas dependence concepts are very useful to describe the relationship between multivariate outcomes, in practice (think for instance to the computation of reinsurance premiums) one need some statistical tool easy to implement, which incorporates the structure of the data. Such tool is the copula, which allows the construction of multivariate distributions for given marginals. Because copulas characterize the dependence structure of random vectors once the effect of the marginals has been factored out, identifying and fitting a copula to data is not an easy task. In practice, it is often preferable to restrict the search of an appropriate copula to some reasonable family, like the archimedean one. Then, it is extremely useful to have simple graphical procedures to select the best fitting model among some competing alternatives for the data at hand. In the second part of the thesis we propose a new nonparametric estimator for the generator, that takes into account the particularity of the data, namely censoring and truncation. This nonparametric estimation then serves as a benchmark to select an appropriate parametric archimedean copula. This selection procedure will be illustrated on a real data set.

Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2008.

An Equivalent Current Injection¡]ECI¡^based Preventive Security- Constrained Optimal Power Flow¡]PSCOPF¡^is presented in this paper and a particle swarm optimization (PSO) algorithm is developed for solving non-convex Optimal Power Flow (OPF) problems. This thesis integrated Simulated Annealing Particle Swarm Optimization¡]SAPSO¡^ and Multiple Particle Swarm Optimization¡]MPSO¡^, enabling a fast algorithm to find the global optimum. Optimal power flow is solved based on Equivalent- Current Injection¡]ECIOPF¡^algorithm. This OPF deals with both continuous and discrete control variables and is a mixed-integer optimal power flow¡]MIOPF¡^. The continuous control variables modeled are the active power output and generator-bus voltage magnitudes, while the discrete ones are the shunt capacitor devices. The feasibility of the proposed method is exhibited for a standard IEEE 30 bus system, and it is compared with other stochastic methods for the solution quality. Security Analysis is also conducted. Ranking method is used to highlight the most severe event caused by a specific fault. A preventive algorithm will make use of the contingency information, and keep the system secure to avoid violations when fault occurs. Generators will be used to adjust the line flow to the point that the trip of the most severe line would not cause a major problem.

La récidive sexuelle est un sujet d’intérêt pour plusieurs chercheurs et intervenants qui travaillent auprès des délinquants sexuels. Afin de mieux prévenir la récidive sexuelle, il importe de bien connaître les causes sous-jacentes à cette problématique. De cette manière, il sera possible d’élaborer des programmes de traitement efficaces et spécifiques à la problématique. Au cours des dernières années, les études sur les prédicteurs de la récidive sexuelle ont mis l’accent essentiellement sur les prédicteurs statiques, mais aussi et de plus en plus sur les prédicteurs dynamiques. Cependant, il ressort de ces études que les caractéristiques inhérentes à l’implication du délinquant à l’intérieur de son programme de traitement ont été peu étudiées. Conséquemment, le but de cette étude est d’analyser les prédicteurs dynamiques de la récidive, l’alliance thérapeutique, la motivation en cours de traitement et le support social en lien à la récidive sexuelle. Pour ce faire, un échantillon de 299 agresseurs sexuels adultes de sexe masculin est pris en considération. Les données pour mener à terme les analyses statistiques sont recueillies avant le début du traitement et en cours de traitement. Trois types de récidive sont considérés : 1) sexuelle, 2) violente, 3) générale. Les variables indépendantes portent sur des outils psychométriques et sont de deux ordres : 1) pré-traitement, 2) en cours de traitement. Deux variables contrôles sont utilisées : 1) traitement complété ou non, 2) type de traitement; cognitivo-comportemental ou mixte. Ainsi, des analyses préliminaires (test T pour groupes indépendants) sont effectuées afin de sélectionner les variables utilisées pour la réalisation des analyses de survie. En raison de la faible prévalence de récidive sexuelle (5,4%), seules les récidives violentes (10,5%) et générales (18,7%) sont considérées. L’étude nous apprend que les résultats aux analyses de survie pour les récidives violentes et générales tendent à être en continuité à celles retrouvées dans les études existantes sur le sujet. Effectivement, l’étude actuelle informe de la pertinence de compléter un programme de traitement comme facteur de protection contribuant à réduire le risque probable de récidive. Le fait de présenter des croyances pédophiliques ou encore, de ne pas présenter de traits de personnalité compulsive sont des facteurs qui contribuent à augmenter les risques relatifs de récidive criminelle. / Repeat sexual offence is a subject of interest for several researchers and workers who intervene with sexual offenders. In order to prevent having second or habitual offenders, it is important to better understand the causes underlying this issue. This will help for the elaboration of more specific and efficient treatment programs. In recent years, research on predictors of sexual recidivism essentially focused on static predictors, but also, and more and more, on dynamic predictors. However, looking at those studies, it is realized that the characteristics of the offender’s participation in his treatment program have not been the subject of much study. Therefore, the goal of the present study is to analyse the dynamic indicators of repeat offence, therapeutic alliance, motivation during treatment and the social support related to repeat sexual offence. For the study, we took a sample of 299 subjects, adult male sexual offenders. Data for the statistical analyses were gathered before and during treatment. Three types of repeat offence are considered: 1) sexual, 2) violent, 3) general. Independent variables are of two kinds: 1) pre-treatment variables, 2) in-treatment variables. Psychometric tools are used here for the independent variables. Two control variables are used: 1) complete or incomplete treatment, 2) type of treatment (cognitive-behavioural versus mixed). Preliminary analyses (T-test for independent groups) were effectuated in order to select the variables to be used in the final analyses. Due to the low rate in regard to repeat sexual offence (5,4%), only violent (18,7%) and general (16%) repeat offences are considered in the final analyses. The study shows that the results for violent and general repeat offences tend to agree with what has been reported in prior studies on the subject. Effectively, the present study informs as to the pertinence of elaborating treatment programs in terms of protection factors so as to reduce the risk of a repeat offence. The fact of holding paedophile beliefs or, still, of not presenting traits of compulsive personality are factors that contribute to increase the risks relatively to a repeat general offence.

Selection and selection procedures play a key role in the ability of organisations to compete successfully in the complex global and local environment. South Africa is experiencing a serious artisinal and technical skill shortage. Given the unemployment issues and the quest for people to fill the skill shortage gap it is important for organizations to find possible solutions to ensure that they stay competitive and effective in the labour market. Research suggests that at least 12 500 artisans need to be produced each year from 2006 to 2010 to meet the demand for skilled workers. To address above mentioned challenge organizations have to develop strategies to assist them to select individuals with the best chance to succeed in training. Unfortunately, the solution is not simple as organisations have a multitude of influences and pressures which affect their decisions regarding selection procedures. Selection of individuals is becoming an increasingly complex science as organisations have to select a capable and representative workforce. They must thus select candidates that are most likely to benefit from what is offered educationally, meet the requirements stipulated in South Africa's Labour legislation, and will perform most successfully in the specific trade. Bad practice can lead to costly litigation. The objectives of this mini-dissertation were to assess the empirical validity of the Technical Test Battery (TTB), as ability test and the Learning Potential Computerised Adaptive Test (LPCAT) as learning potential test as predictors of academic success of first year apprentice electrician students at a South African technical college serving a mining community. The study explored the current local employment issues that affect selection for training in the technical fields. The difference between the measurement of cognitive ability and learning potential were examined and the nature of the constructs of cognitive ability and that of learning potential were discussed. In the empirical study one of the objectives was to determine whether there was a relationship between the TTB and the LPCAT as two different predictors of the academic success of first yar apprentice electrician students. The difference in the empirical (predictive) validity of the two psychometric selection instruments, if only one of the tests as opposed to if both were used in combination, were examined. Another objective was to determine if there were any differences regarding the scores on the TTB and LPCAT of students from the designated group as opposed to that of students from non-designated groups. Finally this study explored whether the TTB and LPCAT were valid predictors to be used as selection instruments for apprentice electrician students in the South African context The research method consisted of a literature review and an empirical study. The empirical validity of the two predictor tests was validated in terms of the accuracy with which the selection instruments predicted the students' future performance. This research can be categorized as descriptive quantitative research. The TTB and LPCAT scores of a sample of 89 selected apprentice electricians were compared with the number of attempts they used to pass a phase test. Data was analysed by means of descriptive statistics. Pearsons Product Moment Correlation Coefficient, t-tests, ANOVAs as well as discriminant analysis were also used to reach the research objective. Statistically significant relationships were found between the predictor and criterion variables. The results confirm that the TTB and LPCAT are indeed empirical valid tests that can be used in the selection of apprentice electricians. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2008.