Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 147-151). Also available online in ProQuest, free to University of Oregon users.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 126-130).

When using control charts to monitor a process it is frequently necessary to simultaneously monitor more than one parameter of the process. Multivariate control charts for monitoring the mean vector, for monitoring variance-covariance matrix and for simultaneously monitoring the mean vector and the variance-covariance matrix of a process with a multivariate normal distribution are investigated. A variable sampling interval (VSI) feature is considered in these charts. Two basic approaches for using past sample information in the development of multivariate control charts are considered. The first approach, which is called the combine-accumulate approach, reduces each multivariate observation to a univariate statistic and then accumulates over past samples. The second approach, which is called the accumulate-combine approach, accumulates past sample information for each parameter and then forms a univariate statistic from the multivariate accumulations. Multivariate control charts are compared on the basis of their average time to signal (ATS) performance. The numerical results show that the multivariate control charts based on the accumulate-combine approach are more efficient than the corresponding multivariate control charts based on the combine-accumulate approach in terms of ATS. Also VSI charts are more efficient than corresponding FSI charts. / Ph. D.

This thesis examines the use of variable sampling intervals as they apply to control charts that use count data. Papers by Reynolds, Arnold, and R. Amin developed properties for charts with an underlying normal distribution. These properties are extended in this thesis to accommodate an underlying Poisson distribution. / Master of Science

An improved quality control model is suggested in this thesis. The improved quality control model is derived by treating the quality control problem as a process control problem. The quality control model is developed by formulating a process control model in terms of product quality parameters and control variables which affect the product quality parameters. SQC is used in the model to provide estimates about the state of the product quality variable as the product is processed by the plant. A state variable approach is used to determine the optimal control strategy. An example quality control model is formulated for a coke size-reduction process. Numerical values are assumed and sensitivity analysis results are discussed. The results show that the proposed quality control model is reasonable. Extensions to more complicated models are discussed. / M.S.

The objectives of this study were to determine the nature of data recorded on the Road to Health Card (RtHC) and its utilisation by nurses at primary health care setting, comparing it with norms and standards on the RtHC guideline, and to provide guidelines for optimal utilisation of the RtHC by health workers. A quantitative nonexperimental descriptive method was used. Two methods were used to collect data; document analysis of the RtHC and structure observation of nurses. A structured exit interview of caregivers was conducted to validate observations from nurses. A sample size of 18 nurses from all categories from six clinics was observed, and 36 RtHC of children under five years of age were analysed. Results indicated that data recorded on the RtHC was mostly inaccurate, incomplete and not interpreted. The study identified a need to train health workers on optimal utilisation of the RtHC facilitating health improvement of children under five years of age. / Health Studies / M.A. (Health Studies)

The objectives of this study were to determine the nature of data recorded on the Road to Health Card (RtHC) and its utilisation by nurses at primary health care setting, comparing it with norms and standards on the RtHC guideline, and to provide guidelines for optimal utilisation of the RtHC by health workers. A quantitative nonexperimental descriptive method was used. Two methods were used to collect data; document analysis of the RtHC and structure observation of nurses. A structured exit interview of caregivers was conducted to validate observations from nurses. A sample size of 18 nurses from all categories from six clinics was observed, and 36 RtHC of children under five years of age were analysed. Results indicated that data recorded on the RtHC was mostly inaccurate, incomplete and not interpreted. The study identified a need to train health workers on optimal utilisation of the RtHC facilitating health improvement of children under five years of age. / Health Studies / M.A. (Health Studies)

The use of external representations (ERs) such as diagrams and animations in science education, particularly in the Molecular Life Sciences (MLS), has rapidly increased over the past decades. Research shows that ERs have a superior advantage over text alone for teaching and learning. Research has also indicated a number of concerns coupled with the use of ERs for education purposes. Such problems emanate from the mode of presentation and/or inability to use ERs. Regarding the later, a number of factors have been identified as major causes of student difficulties and they include visual literacy as one of the major factors. Given that little has been done to understand the nature of VL in the MLS the current study was conducted with the general aim of investigating this area and devising a way to measure the visual literacy levels of our students. More specifically, this study addressed the following research questions: i) What is the nature of visual literacy in MLS?; ii) Can specific levels of visual literacy be defined in the MLS?; and iii) Is a taxonomy a useful way of representing the levels of visual literacy for MLS? To respond to these questions, the current literature was used to define the nature of visual literacy and the visualization skills (VSs). These were then used to develop a Visual Literacy Test made up on probes in the context of Biochemistry. In these probes, the VSs were incorporated. The test was administered to 3rd year Biochemistry students who were also interviewed. Results were analysed qualitatively and quantitatively. The later analysis utilized the Rasch model to generate an item difficulty map. The results of the current study show that visual literacy is multifaceted in nature and is context based in that it requires specific propositional knowledge. In line with this, it was found that visual literacy is expressed through a cognitive process of visualization which requires VSs. Based on the performance of these skills, learners’ optimal visual literacy in the context of the MLS can be defined. Such performance can be assessed through the development of probes in the Biochemistry context. Furthermore, the current research has shown that using probes, the difficulty degree of each VS can be determined. In this instance, the Rasch model is a preferred method of ranking VSs in the context of Biochemistry in order of difficulty. From this, it was shown that given the uniqueness of each skill’s degree of difficulty, each skill can thus be regarded as a level of visual literacy. Such levels were defined in terms of the norm difficulty obtained in the current study. Given the multifaceted nature of visual literacy, the current study adopted the view that there are infinite number of VSs and hence the number of levels of visual literacy. From the variation in the degree of difficulty, the study showed that there are nonvisualization and visualization type difficulties which contribute to the differences in visual literacy levels between Biochemistry students. In addition to this, the current study showed that visual literacy in the MLS can be presented through a taxonomy. Such a taxonomy can be used to determine the level of each VS, its name and definition, typical difficulties found in the MLS as well as the visualization stage at which each skill is performed. Furthermore, this taxonomy can be used to design models, assess students’ visual literacy, identify and inform the remediation of students’ visualization difficulties. While the study has successfully defined the nature of visual literacy for the MLS and presented visual literacy in a taxonomy, more work is required to further understand visual literacy for the MLS, a field where visual literacy is very prevalent. / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2007.

The literature contains conflicting ideas about the effectiveness of diagrams, and their constituent symbolism as teaching and learning tools. In addition, only limited research has been specifically conducted on the presentation and interpretation of arrow symbolism used in biology diagrams, let alone on the nature, source and remediation of student difficulties caused by arrows. On the basis of this limited research and 30 years of experience of teaching biology at secondary-level, the author suspected that students might have difficulties interpreting arrow symbolism in diagrams used as explanatory tools and decided to thoroughly investigate this issue. The hypothesis, 'Secondary-level students have difficulty with the use of arrow symbolism in biology diagrams' was formulated and the following broad research questions defined to address the hypothesis: 1. How much of a problem is arrow symbolism in diagrams? 2. How effectively is arrow symbolism used in diagrams to promote the communication of intended ideas? 3. To what extent does the design of arrow symbolism in diagrams influence students ' interpretation and difficulties? 4. How can the emerging empirical data and ideas from literature be combined to illustrate the process of interpretation of arrow symbolism? 5. What measures can be suggested for improving the presentation and interpretation of arrow symbolism in biology diagrams at secondary-level? To address Research question 1, a content analysis of all arrow symbolism in seven popular secondary-level biology textbooks was undertaken. This revealed a wide diversity of arrow styles, spatial organisations, purposes and meanings that could be confusing to students. These results suggested the need for an evaluation of the effectiveness of arrow symbolism (Research question 2). As there was no definitive set of guidelines available for specifically evaluating arrows, general guidelines from the literature on diagrams were used to develop a set of 10 criteria, to evaluate the syntactic, semantic and pragmatic dimensions of arrow symbolism, which were validated by selected educators, students and a graphic design expert. Application of the criteria (which constituted expert opinion) to the arrow symbolism used in 614 realistic, stylised and abstract diagram types, revealed a relatively high incidence (30%) of inappropriately presented arrow designs that could mislead students. To establish whether this problem could be the cause of student difficulties, and to thereby address Research question 3, a stylised and an abstract diagram were selected and evaluated according to the criteria. The results of the evaluation were compared to the responses given by 174 students to a range of written and interview probes and student modified diagrams. In this way, student performance was correlated with expert opinion. The results confirmed that students experience a wide range of difficulties (26 categories) when interpreting arrow symbolism, with some (12 categories) being attributable to inappropriately presented arrow symbolism and others (14 categories) to student-related processing skills and strategies at both surface- and deeper-levels of reasoning. To address question 4, the emerging empirical data from the evaluation and student studies was combined with a wide range of literature, to inform the development of a 3-level, non-tiered model of the process of interpretation of arrow symbolism in diagrams. As this model emphasised the importance of both arrow presentation in diagrams and arrow interpretation by students, it could be used as an effective explanatory tool as well as a predictive tool to identify sources of difficulty with the use of arrow symbolism. This model was, in turn, used to inform the compilation of a range of guidelines for improving the presentation and interpretation of arrow symbolism, and so target Research question 5. These, and other guidelines grounded in the data and relevant literature, were suggested for all role players, including students, educators, textbook writers, graphic artists and researchers, to use as remedial tools. Future research should focus on the implementation of these guidelines and studying their effectiveness for improving the presentation and interpretation of diagrams with arrow and other types of symbolism. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

This study uses simulation to examine differences between fixed sampling interval (FSI) and variable sampling interval (VSI) Shewhart X-bar control charts for processes that produce positively autocorrelated data. The influence of sample size (1 and 5), autocorrelation parameter, shift in process mean, and length of time between samples is investigated by comparing average time (ATS) and average number of samples (ANSS) to produce an out of control signal for FSI and VSI Shewhart X-bar charts. These comparisons are conducted in two ways: control chart limits pre-set at ±3σ_x / √n and limits computed from the sampling process. Proper interpretation of the Shewhart X-bar chart requires the assumption that observations are statistically independent; however, process data are often autocorrelated over time. Results of this study indicate that increasing the time between samples decreases the effect of positive autocorrelation between samples. Thus, with sufficient time between samples the assumption of independence is essentially not violated. Samples of size 5 produce a faster signal than samples of size 1 with both the FSI and VSI Shewhart X-bar chart when positive autocorrelation is present. However, samples of size 5 require the same time when the data are independent, indicating that this effect is a result of autocorrelation. This research determined that the VSI Shewhart X-bar chart signals increasingly faster than the corresponding FSI chart as the shift in the process mean increases. If the process is likely to exhibit a large shift in the mean, then the VSI technique is recommended. But the faster signaling time of the VSI chart is undesirable when the process is operating on target. However, if the control limits are estimated from process samples, results show that when the process is in control the ARL for the FSI and the ANSS for the VSI are approximately the same, and exceed the expected value when the limits are fixed.