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Split-mouth trials are a design of randomized controlled trial in dentistry in which divisions of the mouth are the units of randomization. Since there is more than one tooth in each mouth division, the structure of the data is complex, which can create difficulties in the statistical analysis. The aim of this study was to determine what is the most appropriate method to analyze split-mouth trials with continuous outcomes, with regards to the treatment effect estimates, power, type-I error, confidence interval coverage and confidence interval width. A superiority split-mouth trial in the field of periodontology was simulated, using two mouth divisions and varying underlying study characteristics such as correlation among teeth, treatment effects and sample size. Twenty-four statistical methods were compared across 315 scenarios. The performance of the statistical methods depended mainly on the correlation among the data, and a paired t-test performed the best across the different scenarios.

Split-mouth trials are a design of randomized controlled trial in dentistry in which divisions of the mouth are the units of randomization. Since there is more than one tooth in each mouth division, the structure of the data is complex, which can create difficulties in the statistical analysis. The aim of this study was to determine what is the most appropriate method to analyze split-mouth trials with continuous outcomes, with regards to the treatment effect estimates, power, type-I error, confidence interval coverage and confidence interval width. A superiority split-mouth trial in the field of periodontology was simulated, using two mouth divisions and varying underlying study characteristics such as correlation among teeth, treatment effects and sample size. Twenty-four statistical methods were compared across 315 scenarios. The performance of the statistical methods depended mainly on the correlation among the data, and a paired t-test performed the best across the different scenarios.

When subjects are recruited through a cross-sectional survey they have already experienced the initiation of the event of interest, say the onset of a disease. This method of recruitment results in the fact that subjects with longer duration of the disease have a higher chance of being selected. It follows that censoring in such a case is not non-informative. The application of standard techniques for right-censored data thus introduces a bias to the analysis; this is referred to as length-bias. This paper examines the case where the subjects are assumed to enter the study at a uniform rate, allowing for the analysis in a more efficient unconditional manner. In particular, a new method for unconditional analysis is developed based on the framework of a conditional estimator. This new method is then applied to the several data sets and compared with the conditional technique of Tsai [23].

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 94-95). Also available via the Internet.

Thesis (Ph. D.)--University of Hong Kong, 1995. / "June 1994." Includes bibliographical references (leave 149-161).

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 11, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. (Tony) Jianguo Sun. Vita. Includes bibliographical references.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2009. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Florida, 1983. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaf 83).

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 2, 2007) Vita. Includes bibliographical references.