baymedr:an R package and web application for the calculation of Bayes factors for superiority, equivalence, and non-inferiority designs

Background: Clinical trials often seek to determine the superiority, equivalence, or non-inferiority of an experimental condition (e.g., a new drug) compared to a control condition (e.g., a placebo or an already existing drug). The use of frequentist statistical methods to analyze data for these types of designs is ubiquitous even though they have several limitations. Bayesian inference remedies many of these shortcomings and allows for intuitive interpretations, but are currently difficult to implement for the applied researcher. Results: We outline the frequentist conceptualization of superiority, equivalence, and non-inferiority designs and discuss its disadvantages. Subsequently, we explain how Bayes factors can be used to compare the relative plausibility of competing hypotheses. We present baymedr, an R package and web application, that provides user-friendly tools for the computation of Bayes factors for superiority, equivalence, and non-inferiority designs. Instructions on how to use baymedr are provided and an example illustrates how existing results can be reanalyzed with baymedr. Conclusions: Our baymedr R package and web application enable researchers to conduct Bayesian superiority, equivalence, and non-inferiority tests. baymedr is characterized by a user-friendly implementation, making it convenient for researchers who are not statistical experts. Using baymedr, it is possible to calculate Bayes factors based on raw data and summary statistics.</p

baymedr: An R Package for the Calculation of Bayes Factors for Equivalence, Non-Inferiority, and Superiority Designs

Clinical trials often seek to determine the equivalence, non-inferiority, or superiority of an experimental condition (e.g., a new drug) compared to a control condition (e.g., a placebo or an already existing drug). The use of frequentist statistical methods to analyze data for these types of designs is ubiquitous. Importantly, however, frequentist inference has several limitations. Bayesian inference remedies these shortcomings and allows for intuitive interpretations. In this article, we outline the frequentist conceptualization of equivalence, non-inferiority, and superiority designs and discuss its disadvantages. Subsequently, we explain how Bayes factors can be used to compare the relative plausibility of competing hypotheses. We present baymedr, an R package that provides user-friendly tools for the computation of Bayes factors for equivalence, non-inferiority, and superiority designs. Detailed instructions on how to use baymedr are provided and an example illustrates how already existing results can be reanalyzed with baymedr.Comment: 33 pages, 3 figure

Russia's Food Trade with the Middle East and North Africa

The Middle East and North Africa (MENA) region is the top destination for Russian food exports. Focusing on Turkey, Egypt, Iran, and Saudi Arabia, this article shows that Russian exports of wheat, barley, and maize are the key component of these bilateral food trade relationships; Russian food imports are typically minor in comparison. Russia’s agricultural trade ties with the MENA countries under study have repeatedly been affected by the improvement and deterioration of political relations. For example, Russia banned most food imports from Turkey over a political conflict in 2016, which prompted counter-measures by the Turkish side. It can generally be observed that Russia is successfully working to open additional destination markets in the region and beyond, while simultaneously impeding imports of specific food products that it aims to produce domestically

Der Aufstieg Russlands zum weltweit größten Weizenexporteur: Bedeutung für den globalen Getreidehandel

Russland ist seit der Jahrtausendwende zum größten Weizenexporteur der Welt aufgestiegen. Während anfangs vor allem Märkte in Nordafrika und dem Nahen Osten bedient wurden, findet russischer Weizen heute vermehrt auch Nachfrage in Subsahara-Afrika und Süd- bzw. Südostasien. Umfangreiche Investitionen in moderne Hafen- und Lagerungseinrichtungen ermöglichen mittlerweile eine gleichmäßig über das Jahr verteilte Getreideausfuhr. Der Weizenexport Russlands ist durch mehrere Besonderheiten geprägt: durch ein stark schwankendes Exportangebot bedingt durch Ernteausfälle und damit verbundene Handelsbeschränkungen, durch Marktintransparenz infolge kaum entwickelter Warenterminmärkte und durch den starken Einfluss des Rubel-Wechselkurses auf die Weizenpreisbildung, mit den entsprechenden negativen Folgen für die Preisvolatilität. Es bleibt abzuwarten, inwieweit die aktuelle Tendenz zur Unternehmenskonzentration im Exportsektor zur Ausübung von Marktmacht und zu Preisverzerrungen führen wird

Selecting feasible trajectories for robot-based X-ray tomography by varying focus-detector-distance in space restricted environments

Computed tomography has evolved as an essential tool for non-destructive testing within the automotive industry. The application of robot-based computed tomography enables high-resolution CT inspections of components exceeding the dimensions accommodated by conventional systems. However, large-scale components, e.g. vehicle bodies, often exhibit trajectory-limiting elements. The utilization of conventional trajectories with constant Focus-Detector-Distances can lead to anisotropy in image data due to the inaccessibility of some angular directions. In this work, we introduce two approaches that are able to select suitable acquisitions point sets in scans of challenging to access regions through the integration of projections with varying Focus-Detector-Distances. The variable distances of the X-ray hardware enable the capability to navigate around collision structures, thus facilitating the scanning of absent angular directions. The initial approach incorporates collision-free viewpoints along a spherical trajectory, preserving the field of view by maintaining a constant ratio between the Focus-Object-Distance and the Object-Detector-Distance, while discreetly extending the Focus-Detector-Distance. The second methodology represents a more straightforward approach, enabling the scanning of angular sectors that were previously inaccessible on the conventional circular trajectory by circumventing the X-ray source around these collision elements. Both the qualitative and quantitative evaluations, contrasting classical trajectories characterized by constant Focus-Detector-Distances with the proposed techniques employing variable Focus-Detector-Distances, indicate that the developed methods improve the object structure interpretability for scans of limited accessibility

Practical Implications of Equating Equivalence Tests:Reply to Campbell and Gustafson (2022)

Linde et al. (2021) compared the "two one-sided tests", the "highest density interval -- region of practical equivalence", and the "interval Bayes factor" approaches to establishing equivalence in terms of power and Type I error rate using typical decision thresholds. They found that the interval Bayes factor approach exhibited a higher power but also a higher Type I error rate than the other approaches. In response, Campbell and Gustafson (2022) showed that the performances of the three approaches can approximate one another when they are calibrated to have the same Type I error rate. In this article, we argue that these results have little bearing on how these approaches are used in practice; a concrete example is used to highlight this important point