Sample size calculation for Mann-Whitney U test with five methods

<p><strong>Background: </strong>Precise sample size estimation plays a vital role in the planning of a study specifically for medical treatment expenses that are expensive and studies that are of high risk.</p><p><strong>Methods: </strong>Among a variety of sample size calculation methods for the nonparametric Mann-Whitney U test, five potential methods are selected for evaluation in this article. The evaluation of method performance is based on the results obtained from high precision Monte Carlo simulations.</p><p><strong>Results: </strong>The sample size deviations (from the simulation ones) are performance indicators. The sum of the squared deviations over all scenarios is used as the criterion for ranking the five methods. For power comparisons, the percentage errors (relative to the simulated powers) are used. The effect size and target power both have large impacts on the minimum required sample sizes.</p><p><strong>Conclusions: </strong>Based on the ranking criterion, Shieh's method has the best performance. Noether's method always overestimates the minimum required sample sizes but not too severe.</p>

Comment on “Aging Population, Retirement, and Risk Taking”

Levy [Levy H (2016) Aging population, retirement, and risk taking. Management Sci. 62(5):1415–1430.] proposes asymptotic first-degree stochastic dominance (AFSD) as a distribution-ranking criterion for all nonsatiable decision makers with infinite investment horizons. By assuming that the terminal wealth follows a log-normal distribution and that the marginal utility is bounded, he offers the necessary and sufficient distributional condition for AFSD. Given Levy’s setting, we provide a counterexample to show that his condition is not necessary and offer the correct equivalent distributional condition for AFSD. This paper was accepted by Karl Diether, finance.

An astrophysically motivated ranking criterion for low-latency electromagnetic follow-up of gravitational wave events

ABSTRACT We investigate the properties of the host galaxies of compact binary mergers across cosmic time. To this end, we combine population synthesis simulations together with galaxy catalogues from the hydrodynamical cosmological simulation eagle to derive the properties of the host galaxies of binary neutron star (BNS), black hole-neutron star (BHNS), and binary black hole (BBH) mergers. Within this framework, we derive the host galaxy probability, i.e. the probability that a galaxy hosts a compact binary coalescence as a function of its stellar mass, star formation rate, Ks magnitude, and B magnitude. This quantity is particularly important for low-latency searches of gravitational wave (GW) sources as it provides a way to rank galaxies lying inside the credible region in the sky of a given GW detection, hence reducing the number of viable host candidates. Furthermore, even if no electromagnetic counterpart is detected, the proposed ranking criterion can still be used to classify the galaxies contained in the error box. Our results show that massive galaxies (or equivalently galaxies with a high luminosity in Ks band) have a higher probability of hosting BNS, BHNS, and BBH mergers. We provide the probabilities in a suitable format to be implemented in future low-latency searches.

COMF: Comprehensive Model-Fitting Method for Simulating Isothermal and Single-Step Solid-State Reactions

It is well known that the implementation of the conventional model-fitting (CMF) method leads to several indistinguishable ‘best’ candidate models (BCMs) for a single-step isothermal solid-state reaction (ISSR), meaning that subjective selection becomes unavoidable. Here, we developed a more robust comprehensive model-fitting method (COMF) which, while maintaining the mathematical simplicity of CMF, utilizes a ranking criterion that enables automatic and unambiguous determination of the BCM. For each model evaluated, COMF, like CMF, fits the integral reaction rate, but, unlike CMF, it also fits the experimental conversion fraction and reaction speed. From this, three different determination coefficients are calculated and combined to rank the considered models. To validate COMF, we used two sets of experimental kinetic data from the literature regarding the isothermal desolvation of pharmaceutical solvates: (i) tetrahydrofuran solvates of sulfameter, and (ii) methanol solvates of ciclesonide. Our results suggest that from an algorithmic perspective, COMF could become the model-fitting method of choice for ISSRs making the selection of BCM easier and more reliable.

RESEARCH OF MULTIPLE INVESTMENT STRATEGIES USING A SHORT AND LONG POSITION

The construction of an optimal portfolio of securities is one of the main tasks of managing the financial system, in which individual assets are only a component part. However, each asset also requires a separate study.I gave the article building an investment portfolio with a zero strategy, comprising borrowing some assets and buying other assets for the same amount. The study comprised choosing the length of the historical horizon, the ranking criterion and the portfolio structure that ensured the maximum investor income.

Engineering Options for an Emission-Free Global Economy by 2050

An overview is presented of the two engineering options which have been offered during the past seven years to accomplish a complete transition to renewable global power generation by 2050. These two approaches are the Wind-Water-Solar program, proposed by Jacobson and Delucchi, and the Energy Ship program, proposed by Platzer and Sarigul-Klijn. A comparative evaluation of the technical, economic and social acceptability aspects of the two options is given. It is argued that the demonstration of techno-economic feasibility needs to be supplemented by an additional ranking criterion, namely the social acceptability factor, in order to select the most promising engineering approach for a successful transition to an emission-free global economy by 2050.

Ranking Two-Stage Production Units in Data Envelopment Analysis

In this paper, we propose a new approach to rank two-stage production systems in data envelopment analysis based on performance of the stages. To do this, a method is devised to compare the stages performance of a special two-stage unit with the corresponding stages performance of other units. The relative performance of two-stage production units is investigated under new definitions of weak and strong relations and a new ranking criterion is introduced as the result. The most important features of our method is the ability to achieve ranking intervals for two-stage production units based on the introduced relations over all feasible weights, as well as the ability to generate accurate information about sources of inefficiency of two-stage production units.