19,434 research outputs found

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    Thesis (M.A.)--Boston Universit

    Stratification Trees for Adaptive Randomization in Randomized Controlled Trials

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    This paper proposes an adaptive randomization procedure for two-stage randomized controlled trials. The method uses data from a first-wave experiment in order to determine how to stratify in a second wave of the experiment, where the objective is to minimize the variance of an estimator for the average treatment effect (ATE). We consider selection from a class of stratified randomization procedures which we call stratification trees: these are procedures whose strata can be represented as decision trees, with differing treatment assignment probabilities across strata. By using the first wave to estimate a stratification tree, we simultaneously select which covariates to use for stratification, how to stratify over these covariates, as well as the assignment probabilities within these strata. Our main result shows that using this randomization procedure with an appropriate estimator results in an asymptotic variance which is minimal in the class of stratification trees. Moreover, the results we present are able to accommodate a large class of assignment mechanisms within strata, including stratified block randomization. In a simulation study, we find that our method, paired with an appropriate cross-validation procedure ,can improve on ad-hoc choices of stratification. We conclude by applying our method to the study in Karlan and Wood (2017), where we estimate stratification trees using the first wave of their experiment

    Video killed the 'PDF' star: taking information resource guides online

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    Easy-to-use technologies now allow librarians to create their own customised digital and video tutorials. This article takes a look at publisher-created video tutorials. It considers the pros and cons of libraries creating their own video-format guides, and elaborates on DCU Library's own experience in producing video-based tutorials on databases customised to local needs using Camtasia and Screentoaster

    Observation of arterial blood pressure of the primate AAP-Bio-A-1 Quarterly progress report, 10 Jul. - 9 Oct. 1968

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    Circuits, components, and implant site evaluations for arterial blood pressure analyses on primate

    QuizPower: a mobile app with app inventor and XAMPP service integration

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    This paper details the development of a mobile app for the Android operating system using MIT App Inventor language and development platform. The app, Quiz Power, provides students a way to study course material in an engaging and effective manner. At its current stage the app is intended strictly for use in a mobile app with App Inventor course, although it provides the facility to be adapted for other courses by simply changing the web data store. Development occurred during the spring semester of 2013. Students in the course played a vital role in providing feedback on course material, which would be the basis for the structure of the quiz as well as the questions. The significance of the project is the integration of the MIT App Inventor service with a web service implemented and managed by the department
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