Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Toronto, 2004. / Includes bibliographical references.

Women are thought to be under-represented as clinical trial participants and as clinical trialists in heart failure. We reviewed randomized controlled trials of heart failure published in high impact medical journals and examined the representation of women as both participants and authors. Furthermore, we explored clinical trial characteristics independently associated with women as clinical trial participants and as lead authors. Our analysis demonstrated that women are under-represented as both clinical trial participants and leaders, with no change in temporal trends over time. Addressing clinical trial characteristics associated with under-representation and developing strategies to overcome barriers may be a strategic way to improve the representation of women in heart failure research. / Thesis / Master of Science (MSc)

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Estimation of exposure-specific risks (ESRs) using estimates of the overall risk and relative risk of disease given exposure has been performed in previous studies, but the performance of such an estimator has not been assessed nor has a variance for such an estimate been proposed. In this project I evaluated the performance of a simple product-based ESR and its variance derived using the delta method. I used the variance to estimate the 95% confidence interval. I found that this point estimate was biased and that the accompanying 95% confidence interval did not attain 95% coverage. I also proposed a revised product-based estimator and found that this estimator was unbiased. I used the delta method to derive a variance for this estimator and estimated the 95% confidence interval. The coverage of this interval attained 95% coverage in most situations. According to the CONSORT statement, subgroup analyses in randomized controlled trials (RCTs) should be pre-planned and accompanied with a formal test of interaction. I considered the interaction between treatment and a dichotomous prognostic factor with a continuous outcome. I examined the impact of misspecifying the distribution of the prognostic factor on power and sample size for interaction effects. I found that power for the interaction test was decreased when the misspecification of the distribution of the prognostic factor was away from a balanced design. I also proposed three methods for improving the power under misspecifications. Quota sampling maintained the power at 80%, but trial completion may be delayed under misspecifications. Modified quota sampling improved the power, but results were related to the proportion of trials switching to the quota sampling procedure. Sample size re-estimation improved the power, but did not always attain 80% power. All three methods maintained appropriate type I error. Lastly, I examined the impact of unplanned cross-over on power and sample size for interaction effects in RCTs. Unplanned cross-over is common in surgical trials and can diminish the magnitude of the interaction effect. Due to this, the sample size re-estimation procedure performed better than quota sampling and modified quota sampling in the presence of unplanned cross-over. / 2031-01-02

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 89-97).

With the wide usage of online tutoring systems, researchers become interested in mining data from logged files of these systems, so as to get better understanding of students. Varieties of aspects of students’ learning have become focus of studies, such as modeling students’ mastery status and affects. On the other hand, Randomized Controlled Trial (RCT), which is an unbiased method for getting insights of education, finds its way in Intelligent Tutoring System. Firstly, people are curious about what kind of settings would work better. Secondly, such a tutoring system, with lots of students and teachers using it, provides an opportunity for building a RCT infrastructure underlying the system. With the increasing interest in Data mining and RCTs, the thesis focuses on these two aspects. In the first part, we focus on analyzing and mining data from ASSISTments, an online tutoring system run by a team in Worcester Polytechnic Institute. Through the data, we try to answer several questions from different aspects of students learning. The first question we try to answer is what matters more to student modeling, skill information or student information. The second question is whether it is necessary to model students’ learning at different opportunity count. The third question is about the benefits of using partial credit, rather than binary credit as measurement of students’ learning in RCTs. The fourth question focuses on the amount that students spent Wheel Spinning in the tutoring system. The fifth questions studies the tradeoff between the mastery threshold and the time spent in the tutoring system. By answering the five questions, we both propose machine learning methodology that can be applied in educational data mining, and present findings from analyzing and mining the data. In the second part, we focused on RCTs within ASSISTments. Firstly, we looked at a pilot study of reassessment and relearning, which suggested a better system setting to improve students’ robust learning. Secondly, we proposed the idea to build an infrastructure of learning within ASSISTments, which provides the opportunities to improve the whole educational environment.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 108-112).

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (p. 86-93).

Source: Dissertation Abstracts International, Volume: 69-10, Section: B, page: 5863. Adviser: Lemuel Moye. Includes bibliographical references.