One key focus in the 21st century is adjusting work and personal life in order for individuals to find a rhythm to help them combine work with other responsibilities and aspirations in their personal lives. Over the past few decades it has become evident that work and personal life are interrelated domains and that employed individuals experience interaction between these domains. Although the amount and extent of work-family research studies in South Africa have progressed considerably over the past decade, it is not clear how the experiences of the interference between work and nonwork roles compare to the experiences of employees in other countries. There is also no South Africa instrument that measures the interference between work and different nonwork roles in both directions (work-to-nonwork and nonwork-to-work). This could pose potential problems for organisations and future workfamily studies in South Africa. The objectives of this research were 1) to gain insight into the interaction between work and personal life in the South African context and how South African employees experience this interaction; 2) to develop a new work-nonwork interference instrument that is suitable for the South African context and that addresses measurement and theoretical issues relating to previous work-family instruments; and 3) to test the psychometric properties of the newly developed work-nonwork interference instrument. The empirical study consisted of three phases. During the first phase, exploratory interviews (i.e. 92 interviews) were conducted in order to gather information regarding the interaction that individuals experience between their work and their personal lives. Thereafter, a new instrument that measures work-nonwork interference was developed and tested with a pilot study (n = 245) in order to overcome some of the measurement limitations relating to previous work-family instruments. During the final phase, the psychometric properties of the newly developed work-nonwork interference instrument were tested (Le. construct validity, discriminant validity, convergent validity and external validity; n = 366). Results from the exploratory phase indicated that South African employees experience various forms of interaction between their work and other dimensions in their personal life (e.g. domestic, leisure, exercise, studies, community, extended family and religion/spirituality). In addition, South African employees experience various stressors in their work environment that contribute to this interaction (i.e. general stressors such as pressure, overload, workload, stressful working arrangements, and strenuous relationships at work, and more occupation-specific stressors such as stressful nature of the job and not being valued in an unsupportive work environment). Additional supportive aspects present in their work environment included supportive work arrangements, supportive relationships at work and occupation satisfaction. Results also indicated consequences specifically related to all the forms of interaction (e.g. time-based consequences, build-up and spillover of emotions, and energy depletion) and consequences that are more related to a specific form of interaction (e.g. mental preoccupation, strain on relationships, managing responsibilities, limiting of work opportunities, energy generation, learned skills). From the exploratory study, very similar findings were obtained and some unique contributions were made to existing workfamily literature. The antecedents mentioned are in line with international literature (physical workload, time pressures, physical stressors, shift work and recipient contact) and the consequences are very similar to categorised consequences reported in international research (i.e. physical, psychological, behavioural, attitudinal, organisational consequences or work, nonwork and health-related consequences). During the second phase a new work-nonwork interference (W-NWI) instrument was developed which differentiates among interference between work and various specific roles in an individuals' personal life (i.e. work-parent interference, parent-work interference, workspouse interference, spouse-work interference, work-religion/spirituality interference, religion/spirituality-work interference, work-domestic interference, domestic-work interference). During the evaluation study various problematic items were eliminated using the Rasch measurement model. The fmal phase included the validation study where the psychometric properties of the new instrument were investigated. The results provided evidence for constrUct, discriminant and convergent validity, reliability and significant relations with external variables. Tills study provides evidence for the psychometric properties of the new instrument, which researchers and managers can use to investigate the specmc interference between work and different nonwork roles in employees' private lives. Recommendations for future research were made. / Thesis (Ph.D. (Industrial Psychology)--North-West University, Potchefstroom Campus, 2010.

With societies aging all around the world, the global burden of degenerative diseases is expected to increase exponentially. From the perspective drug development, degenerative diseases represent an especially challenging class. Clinical trials, in this context often termed disease progression studies, are long, costly, require many individuals, and have low success rates. Therefore, it is crucial to use informative study designs and to analyze efficiently the obtained trial data. The development of novel approaches intended towards facilitating both the design and the analysis of disease progression studies was the aim of this thesis. This aim was pursued in three stages (i) the characterization and extension of pharmacometric software, (ii) the development of new methodology around statistical power, and (iii) the demonstration of application benefits. The optimal design software PopED was extended to simplify the application of optimal design methodology when planning a disease progression study. The performance of non-linear mixed effect estimation algorithms for trial data analysis was evaluated in terms of bias, precision, robustness with respect to initial estimates, and runtime. A novel statistic allowing for explicit optimization of study design for statistical power was derived and found to perform superior to existing methods. Monte-Carlo power studies were accelerated through application of parametric power estimation, delivering full power versus sample size curves from a few hundred Monte-Carlo samples. Optimal design and an explicit optimization for statistical power were applied to the planning of a study in Alzheimer's disease, resulting in a 30% smaller study size when targeting 80% power. The analysis of ADAS-cog score data was improved through application of item response theory, yielding a more exact description of the assessment score, an increased statistical power and an enhanced insight in the assessment properties. In conclusion, this thesis presents novel pharmacometric methods that can help addressing the challenges of designing and planning disease progression studies.

One key focus in the 21st century is adjusting work and personal life in order for individuals to find a rhythm to help them combine work with other responsibilities and aspirations in their personal lives. Over the past few decades it has become evident that work and personal life are interrelated domains and that employed individuals experience interaction between these domains. Although the amount and extent of work-family research studies in South Africa have progressed considerably over the past decade, it is not clear how the experiences of the interference between work and nonwork roles compare to the experiences of employees in other countries. There is also no South Africa instrument that measures the interference between work and different nonwork roles in both directions (work-to-nonwork and nonwork-to-work). This could pose potential problems for organisations and future workfamily studies in South Africa. The objectives of this research were 1) to gain insight into the interaction between work and personal life in the South African context and how South African employees experience this interaction; 2) to develop a new work-nonwork interference instrument that is suitable for the South African context and that addresses measurement and theoretical issues relating to previous work-family instruments; and 3) to test the psychometric properties of the newly developed work-nonwork interference instrument. The empirical study consisted of three phases. During the first phase, exploratory interviews (i.e. 92 interviews) were conducted in order to gather information regarding the interaction that individuals experience between their work and their personal lives. Thereafter, a new instrument that measures work-nonwork interference was developed and tested with a pilot study (n = 245) in order to overcome some of the measurement limitations relating to previous work-family instruments. During the final phase, the psychometric properties of the newly developed work-nonwork interference instrument were tested (Le. construct validity, discriminant validity, convergent validity and external validity; n = 366). Results from the exploratory phase indicated that South African employees experience various forms of interaction between their work and other dimensions in their personal life (e.g. domestic, leisure, exercise, studies, community, extended family and religion/spirituality). In addition, South African employees experience various stressors in their work environment that contribute to this interaction (i.e. general stressors such as pressure, overload, workload, stressful working arrangements, and strenuous relationships at work, and more occupation-specific stressors such as stressful nature of the job and not being valued in an unsupportive work environment). Additional supportive aspects present in their work environment included supportive work arrangements, supportive relationships at work and occupation satisfaction. Results also indicated consequences specifically related to all the forms of interaction (e.g. time-based consequences, build-up and spillover of emotions, and energy depletion) and consequences that are more related to a specific form of interaction (e.g. mental preoccupation, strain on relationships, managing responsibilities, limiting of work opportunities, energy generation, learned skills). From the exploratory study, very similar findings were obtained and some unique contributions were made to existing workfamily literature. The antecedents mentioned are in line with international literature (physical workload, time pressures, physical stressors, shift work and recipient contact) and the consequences are very similar to categorised consequences reported in international research (i.e. physical, psychological, behavioural, attitudinal, organisational consequences or work, nonwork and health-related consequences). During the second phase a new work-nonwork interference (W-NWI) instrument was developed which differentiates among interference between work and various specific roles in an individuals' personal life (i.e. work-parent interference, parent-work interference, workspouse interference, spouse-work interference, work-religion/spirituality interference, religion/spirituality-work interference, work-domestic interference, domestic-work interference). During the evaluation study various problematic items were eliminated using the Rasch measurement model. The fmal phase included the validation study where the psychometric properties of the new instrument were investigated. The results provided evidence for constrUct, discriminant and convergent validity, reliability and significant relations with external variables. Tills study provides evidence for the psychometric properties of the new instrument, which researchers and managers can use to investigate the specmc interference between work and different nonwork roles in employees' private lives. Recommendations for future research were made. / Thesis (Ph.D. (Industrial Psychology)--North-West University, Potchefstroom Campus, 2010.

South African organisations face the challenge of creating organisations that will engage employees in ways that allow for the optimisation of their strengths. This can be achieved by following a strength-based approach (SBA). An SBA aims to achieve optimisation of human functioning, where talents and strengths are the focus and weaknesses are understood and managed. Although previous research suggests that an SBA has positive influences on individual and organisational outcomes, no instrument exists within the South African context that measures employees’ perception of the extent to which they believe their organisation makes use of their strengths and talents. Recently, a new scale was developed to address this need. However, no studies have been done to see how well the items of this scale function. The objectives of this research were to 1) conceptualise an SBA according to literature, 2) determine whether the items in the SBA scale are unidimensional, 3) to determine the internal validity and reliability of the new SBA scale, and 4) make recommendations for future research. A cross-sectional quantitative research design was used whereby online and hardcopy versions of the questionnaire were distributed to participants. A sample of 699 participants was collected from the Gauteng and North-West provinces. Rasch analysis was used to determine the reliability and validity of the items. Acceptable item reliability was found. Both the item and person separation indices were acceptable. Mean infit and outfit indices for both person and item were acceptable. The seven-point frequency-based Likert scale worked satisfactorily overall, although categories 0, 1, and 2 were under-utilised. Finally, the infit and outfit statistics for all eight items functioned satisfactorily, except for one item. Recommendations are made for practice as well as for future research. / Thesis (MA (Industrial Psychology))--North-West University, Potchefstroom Campus, 2012

Pan-Canadian Assessment Program (PCAP) 2007 reading ability item data and contextual data on reading strategies were analyzed to investigate the relationship between self-reported reading strategies and item difficulty. Students who reported using higher- or lower-order strategies were identified through a factor analysis. The purpose of this study was to investigate whether students with the same underlying reading ability but who reported using different reading strategies found the items differentially difficult. Differential item functioning (DIF) analyses identified the items on which students who tended to use higher-order reading strategies excelled, which were selected response items, but students who preferred using lower-order strategies found these items more difficult. The opposite pattern was found for constructed response items. The results of the study suggest that DIF analyses can be used to investigate which reading strategies are related to item difficulty when controlling for students’ level of ability.

Pan-Canadian Assessment Program (PCAP) 2007 reading ability item data and contextual data on reading strategies were analyzed to investigate the relationship between self-reported reading strategies and item difficulty. Students who reported using higher- or lower-order strategies were identified through a factor analysis. The purpose of this study was to investigate whether students with the same underlying reading ability but who reported using different reading strategies found the items differentially difficult. Differential item functioning (DIF) analyses identified the items on which students who tended to use higher-order reading strategies excelled, which were selected response items, but students who preferred using lower-order strategies found these items more difficult. The opposite pattern was found for constructed response items. The results of the study suggest that DIF analyses can be used to investigate which reading strategies are related to item difficulty when controlling for students’ level of ability.

In this study, inventory&ndash / distribution system of a company operating in Fast Moving Consumer Goods (FMCG) industry is analyzed. The system is a multi&ndash / item, two-echelon, divergent inventory&ndash / distribution system with transportation constraints. The warehouses in the system are nonidentical and all of the warehouses are allowed to hold stock. The goal is to achive target customer service levels. Throughout the system, inventory is controlled by echelon stock periodic review (R, S) order-up-to level policy. The problem is the determination of inventory control parameters in the system and effective replenishment of the inventories of many items at regional warehouses under transportation constraints. An approach consisting of three modules operating in a hierarchy is developed to manage the system. The approach calculates the inventory control parameters of the items (order-up-to levels at the regional warehouses and stock allocation fractions) / determines the replenishment periods of the items with the objective of balancing the vehicle requirements among periods and performs the daily replenishment of inventories minimizing the maximum deviation from the inventory policy under transportation constraints. A heuristic approach is adapted from the literature for the inventory control parameter determination part of the approach / an IP model is formulated for the replenishment period scheduling part and a MIP model is constructed for the replenishment process. The proposed approach is simulated with retrospective data of the company and compared with the existing system in the company, in terms of the performance measures defined. Satisfactory results are obtained with the proposed system.

国立情報学研究所で電子化したコンテンツを使用している。

国立情報学研究所で電子化したコンテンツを使用している。

国立情報学研究所で電子化したコンテンツを使用している。