In pursuit of balance : randomization in practice in development field experiments

Randomized experiments are increasingly used in development economics, with researchers now facing the question of not just whether to randomize, but how to do so. Pure random assignment guarantees that the treatment and control groups will have identical characteristics on average, but in any particular random allocation, the two groups will differ along some dimensions. Methods used to pursue greater balance include stratification, pair-wise matching, and re-randomization. This paper presents new evidence on the randomization methods used in existing randomized experiments, and carries out simulations in order to provide guidance for researchers. Three main results emerge. First, many researchers are not controlling for the method of randomization in their analysis. The authors show this leads to tests with incorrect size, and can result in lower power than if a pure random draw was used. Second, they find that in samples of 300 or more, the different randomization methods perform similarly in terms of achieving balance on many future outcomes of interest. However, for very persistent outcome variables and in smaller sample sizes, pair-wise matching and stratification perform best. Third, the analysis suggests that on balance the re-randomization methods common in practice are less desirable than other methods, such as matching.Statistical&Mathematical Sciences,Scientific Research&Science Parks,Science Education,Economic Theory&Research,Climate Change

Mitochondrial DNA Polymerase IB: Functional Characterization of a Putative Drug Target for African Sleeping Sickness

Trypanosoma brucei and related parasites are causative agents of severe diseases that affect global health and economy. T. brucei is responsible for sleeping sickness in humans (African trypanosomiasis) and a wasting disease in livestock. More than 100 years after T. brucei was identified as the etiological agent for sleeping sickness, available treatments remain inadequate, complicated by toxicity, lengthy and expensive administration regiments, and drug-resistance. There is clear need for the development of a new antitrypanosomal drugs. Due to the unique evolutionary position of these early diverging eukaryotes, trypanosomes posses a number of biological properties unparalleled in other organisms, including humans, which could prove valuable for new drug targets. One of the most distinctive properties of trypanosomes is their mitochondrial DNA, called kinetoplast DNA (kDNA). kDNA is composed of over five thousand circular DNA molecules (minicircles and maxicircles) catenated into a topologically complex network. Replication of kDNA requires an elaborate topoisomerase-mediated release and reattachment mechanism for minicircle theta structure replication and at least five DNA polymerases. Three of these (POLIB, POLIC, and POLID) are related to bacterial DNA polymerase I and are required for kDNA maintenance and growth. Each polymerase appears to make a specialized contribution to kDNA replication. The research described in this dissertation is a significant contribution to the field of kDNA replication and the advancement of kDNA replication proteins as putative drug targets for sleeping sickness. Functional characterization of POLIB indicated that it participates in minicircle replication but is likely not the only polymerase contributing to this process. Gene silencing of POLIB partially blocked minicircle replication and led to the production of a previously unidentified free minicircle species, fraction U. Characterization of fraction U confirmed its identity as a population of dimeric minicircles with non-uniform linking numbers. Fraction U was not produced in response to silencing numerous other previously studied kDNA replication proteins but, as we demonstrated here, is also produced in response to POLID silencing. This common phenotype led us to hypothesize that POLIB and POLID both participate in minicircle replication. Simultaneously silencing both polymerases completely blocked minicircle replication, supporting a model of minicircle replication requiring both POLIB and POLID. Finally, we demonstrate that disease-causing trypanosomes require kDNA and the kDNA replication proteins POLIB, POLIC, and POLID. These data provide novel insights into the fascinating mechanism of kDNA replication and support the pursuit of kDNA replication proteins as novel drug targets for combating African trypanosomiasis

Pluralistic landscapes of Northern Roman Britain

Traditional studies of Roman frontiers have focussed on the internal workings of the Roman military or have stressed the continuity of Iron Age society. Such approaches have downplayed or avoided discussions of social interaction. This is in contrast to developments in wider frontier studies in archaeology. This thesis examines pluralistic social settings in the northern frontier area of Roman Britain, addressing the subject in a multiscalar, diachronic, and holistic manner, which incorporates advances made in both Iron Age archaeology and Roman studies.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Influence of primary students’ self-regulated learning profiles on their rating of a technology-enhanced learning environment for mathematics

The importance of learning technologies for mathematics education is increasing as new opportunities arise for mathematics education for all students, in school and at home. These so-called technology-enhanced learning environments (TELEs) incorporating technology with mathematical content are useful for developing mathematical knowledge and can simultaneously foster self-regulated learning (SRL) and motivational learning in mathematics. However, how do primary students’ differences in their SRL and motivation affect their rating of the quality of mathematical TELEs? To answer this research question, we asked third and fourth-grade primary students (n = 115) to evaluate both their SRL, including metacognition and motivation, and the quality characteristics of the ANTON application, a frequently and intensively used TELE in Germany. Using a person-centered research approach by conducting a cluster analysis, we identified three SRL profiles of primary students—motivated self-learners, non-motivated self-learners, and average motivated non-self-learners—who differ in their ratings of the quality characteristics of the TELE (output variables). Our results highlight that motivated self-learners and non-motivated self-learners vary significantly in their rating of the adequacy of the TELE to their mathematical learning and highly but not significantly concerning the TELE’s reward system. Moreover, differences existed between the motivated self-learners and the average motivated non-self-learners regarding their rating of the characteristic differentiation. Based on these findings, we assume that technical elements associated with adequacy, differentiation, and rewards of mathematical TELEs should be tailorable to the needs of individuals and groups of primary schoolchildren

Einschätzungen von Dritt- und Viertklässler*innen zur mathematikdidaktischen Qualität der ANTON-App

Der Einsatz digitaler Medien im Mathematikunterricht ist in der Forschung sowie in der Schulpraxis in den Fokus gerückt und führt zu einem breiten Angebot digitaler Lernangebote wie bspw. unterschiedlicher Tablet-Apps (Rink & Walter, 2020), mit denen Kinder ihre mathematischen Fähigkeiten begleitend zum oder im Unterricht vertiefen können. Eine fachdidaktische Evaluierung dieser Angebote hat bereits in Teilen etwa in Bezug auf die mathematische Lernförderlichkeit (Leuders, 2019) oder auf motivationale und affektive Merkmale (Reinhold et al., 2021) stattgefunden. Darüber hinaus werden weitere systematische Analysen von regelmäßig eingesetzten digitalen Medien benötigt, die zeigen, wie diese das mathematische Lernen von Schüler*innen sinnvoll bereichern können (Bakker, 2018). Als eine der im deutschsprachigen Raum häufig heruntergeladenen und eingesetzten Apps rückt so ANTON - Lernen - Schule (Solocode GmbH, 2021) in den Fokus

Pharmacist-led management of chronic pain in primary care:results from a randomised controlled exploratory trial

To compare the effectiveness of pharmacist medication review, with or without pharmacist prescribing, with standard care, for patients with chronic pain

Clinical effectiveness and cost-effectiveness of open and arthroscopic rotator cuff repair [the UK Rotator Cuff Surgery (UKUFF) randomised trial]

Peer reviewedPublisher PD