No description available.

The test of homogeneity for intraclass correlation coefficients has been one of the active topics in statistical research. Several chi-square tests have been proposed to test the homogeneity of intraclass correlations in the past few decades. The big concern for them is that these methods are seriously biased when sample sizes are not large. In this thesis, data driven approaches are proposed to testing the homogeneity of intraclass correlation coefficients of several populations. Through simulation study, data driven methods have been proved to be less biased and accurate than some commonly used chi-square tests.

This paper uses Maximum likelihood estimation method to estimate the common correlation coefficients for multivariate datasets. We discuss a graphical tool, Q-Q plot, to test equality of the common intraclass correlation coefficients. Kolmogorov-Smirnov test and Cramér-von Mises test are used to check if the intraclass correlation coefficients are the same among populations. Bootstrap and empirical likelihood methods are applied to construct the confidence interval of the common intraclass correlation coefficients.

No description available.

Reliability measures have been well studied over many years, beginning with an entire chapter devoted to intraclass correlation in the first edition of Fisher (1925). Such measures have been thoroughly studied for two factor models. This dissertation, motivated by a medical research problem, extends point and confidence interval estimation of both intraclass correlation coefficient and interater reliability coefficient to models containing three crossed random factors -- subjects, raters and occasions. The intraclass correlation coefficient is used when decision is made on an absolute basis with rater's scores, while the interater reliability coefficient is defined for decisions made on a relative basis. The estimation is conducted using both ANOVA and MCMC methods. The results from the two methods are compared. The MCMC method is preferred for analyses of small data sets when ICC values are high. Besides, the bias of estimator of intraclass correlation coefficient in one-way random effects model is evaluated. / Statistics

The National health and nutrition examination survey (NHANES) is a respected nation-wide program in charge of assessing the health and nutritional status of adults and children in United States. Recent cal research found that folic acid play an important role in preventing baby birth defects. In this paper, we use the generalized estimating equation (GEE) method to study the generalized linear model (GLM) with compound symmetric correlation matrix for the NHANES data and investigate significant factors to ence the intake of food folic acid.

Multilevel datasets are commonly used and increasingly popular in research in the organizational and other social sciences. These models are complex and have many elements beyond those found in more traditional linear models. However, research on how multilevel models perform is lacking. The current paper examined the impact of common factors (average cluster size, cluster size distribution, average number of clusters, strength of the intraclass correlation coefficient, and effect sizes of individual and cluster level variables, and their interaction) in multilevel datasets. Monte Carlo data simulation was used across 6,144 factor-combination conditions. The results of study factors on observed intraclass correlation coefficients, calculated design effect, and empirical design effect are discussed. The results of this study have implications for both researchers in both academic and applied fields. The scale of the simulation variables allow it to be germane to datasets from across the social sciences. However, the nature of data simulation and analysis is such that there are still many elements that can and should be accounted for in future research.

Doctor of Philosophy / Department of Statistics / James Higgins / Many studies are performed on units that cannot be replicated due to cost or other restrictions. There often is an abundance of subsampling to estimate the within unit component of variance, but what is needed for statistical tests is an estimate of the between unit component of variance. There is evidence to suggest that the ratio of the between component of variance to the total variance will remain relatively constant over a range of studies of similar types. Moreover, in many cases this intraclass correlation, which is the ratio of the between unit variance to the total variance, will be relatively small, often 0.1 or less. Such situations exist in education, agriculture, and medicine to name a few. The present study discusses how to use such prior information on the intraclass correlation coefficient (ICC) to obtain inferences about differences among treatments in the face of no replication. Several strategies that use the ICC are recommended for different situations and various designs. Their properties are investigated. Work is extended to under-replicated experiments. The work has a Bayesian flavor but avoids the full Bayesian analysis, which has computational complexities and the potential for lack of acceptance among many applied researchers. This study compares the prior information ICC methods with traditional methods. Situations are suggested in which prior information ICC methods are preferable to traditional methods and those in which the traditional methods are preferable.

Thesis ((Ph.D. (Mathematics Education)) -- University of Limpopo, 2016 / The focus in this thesis was on the approaches that seek to compare two study arms in the absence of randomisation when the interclass correlation coefficient is greater than zero. Many reports on performance of learners in Grade 12 have used ordinary regression models (such as logistic regression model and linear regression models) which ignore clustering effect, and descriptive statistics (e.g., averages and standard deviations for continuous variables, and proportions expressed as percentages and frequencies). These models do not only bias point estimates but also give falsely narrow confidence intervals. The study was applied to two of the nine provinces of South Africa: Gauteng Province and Western Cape Province in 2008, 2009 and 2010 academic years. Causal models, and in particular, hierarchical models (or disaggregated approach), unlike descriptive analyses, are more powerful as they are able to adjust for individual covariates. For the analysis of continuous variables; Western Cape Province was expected to significantly score higher marks than Gauteng Province in 2008 (Crude estimate: 0.782) and 2009 (Crude estimate: 0.957 ) while Gauteng Province was expected to score higher marks than Western Cape Province in 2010 (Crude estimate: −0.302). Adjusted models indicate that Western Cape Province performed better than Gauteng Province in 2008 and 2009 but not in 2010 where Gauteng Province performed better than Western Cape Province after adjusting for gender. In case of binary outcome; the crude estimates favoured Western Cape Province than Gauteng Province in 2008 (Odds ratio = 1.16) and 2009 (Odds ratio = 1.19). Otherwise, the crude estimates favoured Gauteng Province in 2010 (Odds ratio = 0.11). The proportion of female learners in Gauteng Province ranged between 54.48% and 54.99%, while in Western Cape Province it ranged between 56.78% and 57.16%, in 2008 through 2010 academic years. Proportion of female learners in Western Cape Province were found to be higher than those in Gauteng during this period. At least 70.42% of learners in Gauteng and at least 73.96% of learners in Western Cape Province passed Grade 12 during the years 2008 to 2010. Through the application of causal model we have learned that although gender is not a significant predictor of the overall learner performance in Grade 12, the effect of gender gave the mixed findings depending on the nature of the outcome. The xi effect of gender on continuous endpoint (marks) suggests that a model of single-sex classrooms or single-sex schools may be adopted so as to mitigate the inherent perceptions and stereotype regarding learner-gender. However, the results based on binary endpoint (pass/not pass) suggest that coeducation system is the best bet. A school quintile is a significant predictor of the overall learner performance in the two provinces. The resourceful schools are more likely to produce learners with higher marks. Also, the resourced schools than the less or under resourced schools are more likely to produce the favourable results (higher marks (%) or/and pass) in the two provinces.

<p>Introduction</p> <p>The most common complication following invasive cardiac procedures is the development of vascular access site (VAS) bruising. The extent and impact of VAS bruising is poorly understood and minimally reported in the literature. Research into this common post-procedure complication is hindered by the lack of a reliable bruise measurement tool, and the concept that VAS bruising is a minor complication. This mixed methods study examined the inter-rater reliability of two methods to measure VAS bruise size. The embedded qualitative descriptive study explored patient perceptions of VAS bruising.</p> <p>Methods</p> <p>Participants having femoral or radial artery puncture for invasive cardiac procedures were included in this study. Participants reporting VAS bruising completed self measurement of bruise size using two methods, linear measurement and planimetry. The principal investigator and research assistant completed bruise measurements at the same time, and were blinded to participant and each others’ measurements. Following bruise measurement, the principal investigator conducted semi-structured interviews on a convenience sample of participants; including both sexes, a range of ages, and bruise sizes.</p> <p>Results</p> <p>Measurements were completed on 40 participants with VAS bruises. Analysis of inter-rater reliability was done using the intraclass correlation coefficient (ICC), two-way random effects model. The inter-rater reliability for both linear measurement and planimetry between all three measurers was high (.929; .914 respectively). Analysis of participant narratives uncovered three major themes concerns, impact and mediating factors, with several sub-themes.</p> <p>The findings of this study support the reliability of patient VAS bruise measurement using linear measurement and planimetry. The goals and available resources for VAS research may determine the choice of measurement approach. Qualitative descriptive results indicate that patients have concerns related to VAS bruising and that this bruising may impact activities of daily living. Future research examining VAS complications should include evaluation of VAS bruising as significant patient outcome.</p> / Doctor of Philosophy (PhD)