UWCScholar :: Browsing by Author "Blignaut, Renette"

Browsing by Author "Blignaut, Renette"

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An application of factor analysis on a 24-item scale on the attitudes towards AIDS precautions using Pearson, Spearman and Polychoric correlation matrices
(University of the Western Cape, 2006) Abdalmajid, Mohammed Babekir Elmalik; Blignaut, Renette; Dept. of Statistics; Faculty of Science
The 24-item scale has been used extensively to assess the attitudes towards AIDS precautions. This study investigated the usefulness and validity of the instrument in a South African setting, fourteen years after the development of the instrument. If a new structure could be found statistically, the HIV/AIDS prevention strategies could be more effective in aiding campaigns to change attitudes and sexual behaviour.
Assessing the high-risk behaviour of first year students entering the University of the Western Cape
(University of the Western Cape, 2007) Abels, Melissa Dione; Blignaut, Renette; Doctor, V; Dept. of Statistics; Faculty of Science
The motivation of this study is to assess the high risk behaviors that contribute to the spread of HIV and AIDS among the youth. The most influential high risk behaviours that contribute to the spread of HIV and AIDS are unprotected sexual intercourse and having more than one sexual partner.The population for this study includes all full time first year students who registered for the first time in 2006 that attended the orientation week. A stratified, sequential random sample was drawn from the students attending the orientation.
A bridge over the computer science graduate skill gap
(2013) Blignaut, Renette; Venter, Isabella M.; Renaud, Karen
Universities are increasingly required to respond to the ever evolving needs of an ever more sophisticated and globalised workplace, which requires well-rounded workers with more than mere technical knowledge. Employers expect their prospective employees to already have acquired a range of professional and personal skills. Universities face a challenge in helping students to develop these skills and it is debatable whether this can be achieved within the university environment. What is needed is a way for students to interact with the outside world as part of their undergraduate programme in a situated learning environment. This paper reports on a computer science assignment specifically designed to develop professional and personal as well as discipline-specific skills. The results suggest that situated learning assignments are indeed able to enhance the development of precisely those soft skills which are so valued by employers.
Comparative study of admissions criteria of a selection of South African universities
(Stellenbosch University, 2011) Blignaut, Renette; Venter, Isabella M.
Summary: The new school-leaving certificate, the National Senior Certificate (NSC), was awarded for the first time in 2008. This necessitated a relook at the entrance requirements for university, as the school subjects offered, and the evaluation thereof, had changed considerably compared with those for the previous schoolleaving certificate (Senior Certificate). It became important for universities to adjust their admission requirements from the 2009 firstyear intake onwards. The admission requirements of nine universities (considered by FinWeek, 18 March 2010, to be similar in terms of effectiveness and classification) were compared. The universities are: the University of the Free State (UOFS), the University of the Western Cape (UWC/WestCapU), the University of KwaZuluNatal (UKZN), the University of Pretoria (UP/UPret), NorthWest University (NWU/NWestU), the University of the Witwatersrand (WITS/UWits), the University of Cape Town (UCT), Rhodes University (Rhodes/RhodesU) and the University of Stellenbosch (US/UStell). (The second abbreviation appearing in some cases is the abbreviation used in Figure 1, which was taken directly from Finweek.) Effectiveness is defined by FinWeek as a combination of the following: undergraduate success rate; graduates as percentage of total enrolment; research output units and contracted research, while classification of institutions is defined as a range from mainly undergraduate training institutions to mainly researchled institutions. This study considered how the nine selected South African universities utilise the NSC results to select students for their mathematical statistics and computer science degrees. Some of the universities use only the NSC results for placement, while others use a combination of the NSC results and some additional admission tests. At most universities the NSC results are combined into an admission point score (APS). This APS is calculated differently at the different universities. The following questions were investigated:  How is the APS calculated by each of the nine universities considered in this study?  What minimum APS is required for general entrance to undergraduate studies at these universities?  What minimum APS do students need to enter a three-year programme in mathematical statistics or computer science at these nine universities? To compare the admission requirements of the universities considered, the entrance requirements documents of the various universities were studied and compared. Furthermore, secondary data of the University of the Western Cape were used to illustrate the differences in the APSs for these universities. A sample of 176 students who matriculated in 2008 with six or more designated NSC subjects and who were in their first year at UWC in 2009 was considered for this study. The UWC data were used to calculate the APSs according to the 2011 admission requirements of the nine universities. In general, students have to offer a minimum of four subjects from the designated subject list, with a level 4 (≥50 percent) or more, to qualify for university admission. For this study only students who had completed six or more designated subjects were considered. To further contain the study, only students that could possibly have qualified for a mathematical statistics or computer science degree were considered. These programmes require school mathematics and not mathematical literacy as a subject. Both these programmes are offered at all the universities considered in this study and could, therefore, be compared. The method for calculating the APS differs substantially between the universities, as does the minimum score required for university admission. To compare the minimum required APS for admission to the respective selected universities the research data of 176 UWC students were used. It was found that only 11 percent of the 176 students admitted to UWC would have qualified for admission at UCT. Although UWC and Rhodes use similar methods for calculating their APSs they have very different minimum APS requirements: Rhodes requires an APS of 40, whereas UWC requires an APS of only 27. Consequently Rhodes would have accepted only 18 percent of the students that were accepted by UWC. Due to the stricter mathematics requirement for the programmes considered, fewer students qualify for these programmes than would have qualified for general university admission. In order to see what APS would be necessary for a student studying at UWC to successfully complete a first year, the 2009 end-of-year university results of the 176 students of this pilot study were used. Of the 176 UWC students that started their studies in 2009, only 108 (61 percent) progressed to the next academic year in 2010. Their average UWC APS was 41,4 with a 95 percent confidence interval of (40,4; 42,3). If a simplified method is used for calculating the APS, namely summing the school scores (without life orientation (LO)), the 95 percent confidence interval for the mean APS of the students that progressed is (30,4; 32,1). It needs to be noted that both UWC and Rhodes use a more complex method of calculating the APS which inflates the APS by approximately 10 points. Currently universities differ considerably in their calculation of the APS as well as their minimum entrance requirements. A simplified and standardised method for the calculation of the APS would allow learners and other stakeholders to easily determine the APS required to be selected for a particular tertiary programme. For most programmes further school subject requirements are specified. For the mathematical statistics and computer science programmes at the universities studied, the difference in the school mathematics requirement is most pronounced. According to this pilot study the APS a student requires to successfully complete the first academic year at UWC, is approximately 30 when the simplified method to calculate the APS is used (summing the scores of six designated school subjects (without LO)). An APS of 30 is currently being used by UP, UKZN and UFS as the minimum requirement for selection. Their method of calculating the APS is very similar to the method proposed by this study. Additional studies would need to be carried out to confirm the results of this pilot study. Further studies are also needed to determine how the scores of the nondesignated subjects should be adjusted for possible inclusion in the calculation of the APS. The NSC is now standardised across South Africa. If the APS is also calculated in a standardised manner it should be sufficient to use this information to determine which students would be able to succeed at university. The minimum admission requirement could vary from university to university depending on the programme for which a student applies. The minimum APS for a programme should be carefully considered and adjusted so that selected students have a chance to succeed. If academically underprepared students are selected for tertiary studies the universities should be aware that these students will need extensive extracurricular assistance. Without additional interventions these underprepared students will have no chance of succeeding at university, which is ethically unjustifiable.
Correlates of gender characteristics, health and empowerment of women in Ethiopia
(BMC, 2015) Lailulo, Yishak Abraham; Susuman, Sathiya A.; Blignaut, Renette
The low status of women prevents them from recognizing and voicing their concerns about health needs. This study aimed to examine the relationship between gender characteristics, health and empowerment of women in an attempt to understand between 2005 and 2011. Data from the Ethiopia Demographic and Health Survey (EDHS) 2005 and 2011 were used. Bivariate and multivariate analyses were used to determine the relative contribution of the predictor variables. The hypotheses tested in this study were that gender (men and women), health and empowerment of women in region are highly significant with women’s education and work status. Study findings showed that the low status of women and their disempowerment are highly associated with poor health outcomes. In both 2005 and 2011 men school ages were positively associated with their attainment in primary education, whereas for women it was negatively related with their attainment in some education. In both 2005 and 2011 women in the richest wealth quintile had the highest odds ratio of relating to some education.
Designing mobile phone interfaces for age diversity in South Africa: “One-World” versus diverse “Islands”
(Springer, 2013) Renaud, Karen; Blignaut, Renette; Venter, Isabella M.
Designing for diversity is a laudable aim. How to achieve this, in the context of mobile phone usage by South African seniors, is a moot point. We considered this question from two possible perspectives: universal (one-world) versus focused design (designing for diverse “islands” of users). Each island would be characterised by a measure of relative homogeneity in terms of user interface needs. Our particular focus in this paper is age diversity. The universal approach attempts to deliver a design that can be all things to all people – meeting the needs of all users within one user interface. The islander approach delivers specific and different designs for islands within a diverse world. To determine which the best approach would be, in the South African context, we dispatched a team of student researchers to interview participants from an older generation, on a one-to-one basis. It was beneficial to deploy aspiring designers to carry out this research because we wanted to confront aspiring researchers with the differences between their own and other generations’ usage of, and attitudes towards, mobile phones. Our study found that there were indeed significant age-related differences in mobile phone usage. Our research delivered insights that led to a model of the factors impacting mobile phone usage of the senior generation as a series of filters between the user and their device. We conclude that the island approach is more suitable for age-specific design. This approach might well become less fitting as a more technologically experienced population ages, but at present there is a clear need for an agesensitive mobile interface design.
Fast tracking students from disadvantaged backgrounds into main stream Computer Science
(Computer Society of South Africa, 2000) Blignaut, Renette; Venter, Isabella M.; Cranfield, D.J.
A computer-based training (CBT) system was used to teach Computer Literacy to full-time students at the University of the Western Cape. This approach was successful in creating computer literate students as well as creating an opportunity for students from educationally disadvantaged schools to enter the Computer Science course. The students experienced this new approach to learning positively. This has laid the foundation to export the computer-based education model to communities outside the university. Lifelong learning opportunities will thus be created.
Fitting extreme value distributions to the Zambezi river flood water levels recorded at Katima Mulilo in Namibia
(University of the Western Cape, 2005) Kamwi, Innocent Silibelo; Koen, C; Blignaut, Renette; Dept. of Statistics; Faculty of Science
The aim of this research project was to estimate parameters for the distribution of annual maximum flood levels for the Zambezi River at Katima Mulilo. The estimation of parameters was done by using the maximum likelihood method. The study aimed to explore data of the Zambezi's annual maximum flood heights at Katima Mulilo by means of fitting the Gumbel, Weibull and the generalized extreme value distributions and evaluated their goodness of fit.
Granny gets smarter but junior hardly notices
(College of Communication and Information, 2016) Blignaut, Renette; Venter, Isabella Margarethe; Renaud, Karen
To ensure that university computing students are sensitized to the needs of diverse user groups, a course project was designed to allow students to get a realistic understanding of the needs and abilities of the older mobile phone user. Over a three year period different student cohorts interviewed these users to assess their experience with mobile phones. It was found that students were generally dismissive of the cognitive abilities of the older mobile phone user. However the yearly snapshot revealed that the older user’s abilities improved year on year. Being prepared to understand all user groups is an essential skill that should be acquired by future interface designers.
Improving maternal and reproductive health in Ethiopia
(Sage Publications, 2017) Lailulo, Yishak Abraham; Appunni, Sathiya Susuman; Blignaut, Renette
This study aimed to examine the relationship between maternal health and good quality of life in an attempt to understand the years between 2005 and 2011. Data from the Ethiopia Demographic and Health Surveys 2005 and 2011 were used. Bivariate, Camer-V, chi-square and logistic regression analyses were used to determine the relative contribution of the predictor variables. The hypotheses tested in this study were that gender, wealth quintile, type of place of residence and region are highly significant with women’s education and work status. Females’ expected age (adjusted odds ratio = AOR) for some school training has dropped in 2011 from 0.678 to 0.255 for the age group 25–34, but male expected age (AOR) for some school has increased in 2011 from 0.784 to 2.274. The age of the respondent, age at first cohabitation and socio-economic variables were positively associated with having visited health facilities in the last 12 months and being visited by a family planning worker.
Imputation techniques for non-ordered categorical missing data
(University of the Western Cape, 2016) Karangwa, Innocent; Kotze, Danelle; Blignaut, Renette
Missing data are common in survey data sets. Enrolled subjects do not often have data recorded for all variables of interest. The inappropriate handling of missing data may lead to bias in the estimates and incorrect inferences. Therefore, special attention is needed when analysing incomplete data. The multivariate normal imputation (MVNI) and the multiple imputation by chained equations (MICE) have emerged as the best techniques to impute or fills in missing data. The former assumes a normal distribution of the variables in the imputation model, but can also handle missing data whose distributions are not normal. The latter fills in missing values taking into account the distributional form of the variables to be imputed. The aim of this study was to determine the performance of these methods when data are missing at random (MAR) or completely at random (MCAR) on unordered or nominal categorical variables treated as predictors or response variables in the regression models. Both dichotomous and polytomous variables were considered in the analysis. The baseline data used was the 2007 Demographic and Health Survey (DHS) from the Democratic Republic of Congo. The analysis model of interest was the logistic regression model of the woman’s contraceptive method use status on her marital status, controlling or not for other covariates (continuous, nominal and ordinal). Based on the data set with missing values, data sets with missing at random and missing completely at random observations on either the covariates or response variables measured on nominal scale were first simulated, and then used for imputation purposes. Under MVNI method, unordered categorical variables were first dichotomised, and then K − 1 (where K is the number of levels of the categorical variable of interest) dichotomised variables were included in the imputation model, leaving the other category as a reference. These variables were imputed as continuous variables using a linear regression model. Imputation with MICE considered the distributional form of each variable to be imputed. That is, imputations were drawn using binary and multinomial logistic regressions for dichotomous and polytomous variables respectively. The performance of these methods was evaluated in terms of bias and standard errors in regression coefficients that were estimated to determine the association between the woman’s contraceptive methods use status and her marital status, controlling or not for other types of variables. The analysis was done assuming that the sample was not weighted fi then the sample weight was taken into account to assess whether the sample design would affect the performance of the multiple imputation methods of interest, namely MVNI and MICE. As expected, the results showed that for all the models, MVNI and MICE produced less biased smaller standard errors than the case deletion (CD) method, which discards items with missing values from the analysis. Moreover, it was found that when data were missing (MCAR or MAR) on the nominal variables that were treated as predictors in the regression model, MVNI reduced bias in the regression coefficients and standard errors compared to MICE, for both unweighted and weighted data sets. On the other hand, the results indicated that MICE outperforms MVNI when data were missing on the response variables, either the binary or polytomous. Furthermore, it was noted that the sample design (sample weights), the rates of missingness and the missing data mechanisms (MCAR or MAR) did not affect the behaviour of the multiple imputation methods that were considered in this study. Thus, based on these results, it can be concluded that when missing values are present on the outcome variables measured on a nominal scale in regression models, the distributional form of the variable with missing values should be taken into account. When these variables are used as predictors (with missing observations), the parametric imputation approach (MVNI) would be a better option than MICE.
An in-depth study of the ICT ecosystem in a South African rural community: unveiling expenditure and communication patterns
(Routledge, 2016) Rey-Moreno, Carlos; Blignaut, Renette; May, Julian; Tucker, William David
There is no doubt of the contributions made by mobile phones and mobile network operators in increasing access to communications in rural areas of developing countries. Yet how affordable is this ubiquitous access in such an ICT ecosystem? Using data from two stratified random surveys conducted in a South African rural community, this paper provides a unique in-depth picture of the expenditure and communication patterns of its dwellers. Results show a high access ratio of people using mobile phone services weekly and a high proportion of disposable income dedicated to a very constrained set of mobile phone services. Factors such as mobile phone charging and the extra charges added by airtime resellers contribute to increase the communication costs. This data and its analysis can be used by the following: regulators and government agencies to better design their policy implementations to provide universal service and access; competing industry players to understand the dynamics within rural communities to better target their products; civil society organizations to a constitutional right.
Maths4Stats: Opleiding vir onderwysers
(AOSIS, 2013) Blignaut, Renette; Luus, Retha; Lombard, Ronell; Latief, Abduraghiem; Kotze, Danelle
Maths4Stats: Educating teachers. The inadequate nature of the education infrastructure in South Africa has led to poor academic performance at public schools. Problems within schools such as under-qualified teachers and poor teacher performance arise due to the poorly constructed education system in our country. The implementation in 2012 of the Curriculum and Assessment Policy Statement (CAPS) at public schools in South Africa saw the further crippling of some teachers, as they were unfamiliar with parts of the CAPS subject content. The Statistics and Population Studies department at the University of the Western Cape was asked to join the Maths4Stats project in 2012. This project was launched by Statistics South Africa in an effort to assist in training the teachers in statistical content within the CAPS Mathematics curricula. The University of the Western Cape's team would like to share their experience of being part of the Maths4Stats training in the Western Cape. This article focuses on how the training sessions were planned and what the outcomes were. With the knowledge gained from our first Maths4Stats experience, it is recommended that future interventions are still needed to ensure that mathematics teachers become well-informed and confident to teach topics such as data handling, probability and regression analysis.
Missing imputation methods explored in big data analytics
(University of the Western Cape, 2018) Brydon, Humphrey Charles; Blignaut, Renette
The aim of this study is to look at the methods and processes involved in imputing missing data and more specifically, complete missing blocks of data. A further aim of this study is to look at the effect that the imputed data has on the accuracy of various predictive models constructed on the imputed data and hence determine if the imputation method involved is suitable. The identification of the missingness mechanism present in the data should be the first process to follow in order to identify a possible imputation method. The identification of a suitable imputation method is easier if the mechanism can be identified as one of the following; missing completely at random (MCAR), missing at random (MAR) or not missing at random (NMAR). Predictive models constructed on the complete imputed data sets are shown to be less accurate for those models constructed on data sets which employed a hot-deck imputation method. The data sets which employed either a single or multiple Monte Carlo Markov Chain (MCMC) or the Fully Conditional Specification (FCS) imputation methods are shown to result in predictive models that are more accurate. The addition of an iterative bagging technique in the modelling procedure is shown to produce highly accurate prediction estimates. The bagging technique is applied to variants of the neural network, a decision tree and a multiple linear regression (MLR) modelling procedure. A stochastic gradient boosted decision tree (SGBT) is also constructed as a comparison to the bagged decision tree. Final models are constructed from 200 iterations of the various modelling procedures using a 60% sampling ratio in the bagging procedure. It is further shown that the addition of the bagging technique in the MLR modelling procedure can produce a MLR model that is more accurate than that of the other more advanced modelling procedures under certain conditions. The evaluation of the predictive models constructed on imputed data is shown to vary based on the type of fit statistic used. It is shown that the average squared error reports little difference in the accuracy levels when compared to the results of the Mean Absolute Prediction Error (MAPE). The MAPE fit statistic is able to magnify the difference in the prediction errors reported. The Normalized Mean Bias Error (NMBE) results show that all predictive models constructed produced estimates that were an over-prediction, although these did vary depending on the data set and modelling procedure used. The Nash Sutcliffe efficiency (NSE) was used as a comparison statistic to compare the accuracy of the predictive models in the context of imputed data. The NSE statistic showed that the estimates of the models constructed on the imputed data sets employing a multiple imputation method were highly accurate. The NSE statistic results reported that the estimates from the predictive models constructed on the hot-deck imputed data were inaccurate and that a mean substitution of the fully observed data would have been a better method of imputation. The conclusion reached in this study shows that the choice of imputation method as well as that of the predictive model is dependent on the data used. Four unique combinations of imputation methods and modelling procedures were concluded for the data considered in this study.
A multilevel analysis of learner and school contextual factors associated with educational quality
(2013) Winnaar, Lolita; Blignaut, Renette; Frempong, G.
The South African schools act, (number 5, 1996), asserts that all learners have a right to access both basic and quality education without discrimination of any sort. Since the implementation of the Millennium Development Goals there has been a drive by the Department of Education to ensure that all learners have access to basic education by 2015. However what remains a challenge after almost 20 years of democracy is the poor quality of education and this is clear from the results of international assessment studies. Results from studies like the Trends in International Mathematics and Science Study and Southern and East Africa Consortium for Monitoring Educational Quality, show that South African children perform well below international averages. In this study learner Mathematics achievement scores taken from the Trends in International Mathematics and Science Study 2011 cycle will serve as a proxy for educational quality. Using multilevel analysis the current study aims to use a 2-level Hierarchical Linear Model to firstly; determine the learner and family background factors associated with education quality. Secondly; factors at the school level will be identified and proven to be associated with education quality. Variables selected for the study was based on Creamer’s theory of school effectiveness which looked at school, classroom level inputs as well as learner background variables to explain student level achievement. The results show that at the learner’s level the most significant factors were the age of the leaner, in the sense that grade age appropriate learners obtained higher scores than overage learners. Learner’s perception of mathematics is extremely important and has a positive effect on mathematics performance. In the current study mathematics perception refers to learners valuing and liking mathematics as well learner confidence in learning mathematics. Learners who said they were bullied as school generally scored lower than learners who were not bullied. At the school level the most significant factors were teacher working conditions, teachers’ specialisation in mathematics, school socio-economic status, and general infrastructure. Interesting to note at the school level is when socioeconomic status was included in the model as a single variable the score difference between low socio-economic status and high socio-economic status schools was almost 46 points. However when the factors mentioned above were added to the model the difference in scores dropped by almost half.
Multiple imputation of unordered categorical missing data: A comparison of the multivariate normal imputation and multiple imputation by chained equations
(Brazilian Statistical Association, 2016) Karangwa, Innocent; Kotze, Danelle; Blignaut, Renette
. Missing data are common in survey data sets. Enrolled subjects do not often have data recorded for all variables of interest. The inappropriate handling of them may negatively affect the inferences drawn. Therefore, special attention is needed when analysing incomplete data. The multivariate normal imputation (MVNI) and the multiple imputation by chained equations (MICE) have emerged as the best techniques to deal with missing data. The former assumes a normal distribution of the variables in the imputation model and the latter fills in missing values taking into account the distributional form of the variables to be imputed. This study examines the performance of these methods when data are missing at random on unordered categorical variables treated as predictors in the regression models. First, a survey data set with no missing values is used to generate a data set with missing at random observations on unordered categorical variables.
Perceived quality and utilisation of maternal health services in peri-urban, commercial farming, and rural areas in South Africa
(University of the Western Cape, 2006) Matizirofa, Lyness; Jackson, D; Blignaut, Renette; Dept. of Statistics; Faculty of Science
This investigation aimed to determine factors that influence women's utilisation of maternal health services, with specific focus on the quality of care and services available to disadvantaged communities in South Africa. It used the women's perspectives to assess the quality of maternal healthcare services in peri-urban commercial farming and rural areas with the purpose of understanding why women utilise maternal services the way they do.
Quantified assessment to enhance student learning in the sciences at UWC
(University of the Western Cape, 2005) Lombard, Ronell; Blignaut, Renette; Dept. of Biotechnology; Faculty of Science
This project discusses whether the British prototype questionnaire called the Assessment Experience Questionnaire (AEQ) could be standardized as a quantifier of assessment and be used at a multicultural institute such as the University of the Western Cape (UWC). This questionnaire was created in the United Kingdom to assist lecturers in evaluating and developing their assessment systems.
Smartphone owners need security advice. How can we ensure they get it?
(CONF-IRM and AIS Electronic Library (AISeL), 2016) Renaud, Karen; Blignaut, Renette; Venter, Isabella
Computer users often behave insecurely, and do not take the precautions they ought to. One reads almost daily about people not protecting their devices, not making backups and falling for phishing messages. This impacts all of society since people increasingly carry a computer in their pockets: their smartphones. It could be that smartphone owners simply do not know enough about security threats or precautions. To address this, many official bodies publish advice online. For such a broadcast-type educational approach to work, two assumptions must be satisfied. The first is that people will deliberately seek out security-related information and the second is that they will consult official sources to satisfy their information needs. Assumptions such as these ought to be verified, especially with the numbers of cyber attacks on the rise. It was decided to explore the validity of these assumptions by surveying students at a South African university, including both Computer Science and Non-Computer Science students. The intention was to explore levels of awareness of Smartphone security practice, the sources of advice the students used, and the impact of a Computer Science education on awareness and information seeking behaviours. Awareness, it was found, was variable across the board but poorer amongst students without a formal computing education. Moreover, it became clear that students often found Facebook more helpful than public media, in terms of obtaining security advice.
The statistical theory underlying human genetic linkage analysis based on quantitative data from extended families
(University of the Western Cape, 2010) Galal, Ushma; van der Merwe, Lize; Blignaut, Renette; Dept. of Statistics; Faculty of Science
Traditionally in human genetic linkage analysis, extended families were only used in the analysis of dichotomous traits, such as Disease/No Disease. For quantitative traits, analyses initially focused on data from family trios (for example, mother, father, and child) or sib-pairs. Recently however, there have been two very important developments in genetics: It became clear that if the disease status of several generations of a family is known and their genetic information is obtained, researchers can pinpoint which pieces of genetic material are linked to the disease or trait. It also became evident that if a trait is quantitative (numerical), as blood pressure or viral loads are, rather than dichotomous, one has much more power for the same sample size. This led to the development of statistical mixed models which could incorporate all the features of the data, including the degree of relationship between each pair of family members. This is necessary because a parent-child pair definitely shares half their genetic material, whereas a pair of cousins share, on average, only an eighth. The statistical methods involved here have however been developed by geneticists, for their specific studies, so there does not seem to be a unified and general description of the theory underlying the methods. The aim of this dissertation is to explain in a unified and statistically comprehensive manner, the theory involved in the analysis of quantitative trait genetic data from extended families. The focus is on linkage analysis: what it is and what it aims to do. There is a step-by-step build up to it, starting with an introduction to genetic epidemiology. This includes an explanation of the relevant genetic terminology. There is also an application section where an appropriate human genetic family dataset is analysed, illustrating the methods explained in the theory sections.

Browsing by Author "Blignaut, Renette"

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