Resolving conflicts between statistical methods by probability combination: Application to empirical Bayes analyses of genomic data

In the typical analysis of a data set, a single method is selected for statistical reporting even when equally applicable methods yield very different results. Examples of equally applicable methods can correspond to those of different ancillary statistics in frequentist inference and of different prior distributions in Bayesian inference. More broadly, choices are made between parametric and nonparametric methods and between frequentist and Bayesian methods. Rather than choosing a single method, it can be safer, in a game-theoretic sense, to combine those that are equally appropriate in light of the available information. Since methods of combining subjectively assessed probability distributions are not objective enough for that purpose, this paper introduces a method of distribution combination that does not require any assignment of distribution weights. It does so by formalizing a hedging strategy in terms of a game between three players: nature, a statistician combining distributions, and a statistician refusing to combine distributions. The optimal move of the first statistician reduces to the solution of a simpler problem of selecting an estimating distribution that minimizes the Kullback-Leibler loss maximized over the plausible distributions to be combined. The resulting combined distribution is a linear combination of the most extreme of the distributions to be combined that are scientifically plausible. The optimal weights are close enough to each other that no extreme distribution dominates the others. The new methodology is illustrated by combining conflicting empirical Bayes methodologies in the context of gene expression data analysis

Social Media and Depressive Symptoms in Childhood and Adolescence: A Systematic Review

Concerns are increasingly raised in academic and lay literature about the impact of the internet on young people’s well-being. This systematic review examined empirical research on the relationship between social media use and depressive symptoms in the child and adolescent population. A systematic search of Medline, PsycInfo and Embase databases yielded eleven eligible studies. Relevant results were extracted from each study, with a total sample of 12,646. Analysis revealed a small but statistically significant correlation between social media use and depressive symptoms in young people. However, studies varied widely in methods, sample size and results, making the clinical significance of these findings nuanced. Over half of the studies were cross-sectional, while those of longitudinal design were of limited duration. This review justifies further investigation of this phenomenon, with a need for consensus on variables and measurement

Ants Sow the Seeds of Global Diversification in Flowering Plants

Background: The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000–300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances. Methodology/Principal Findings: Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions. Conclusions/Significance: Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on largescale diversification

Justify your alpha

Benjamin et al. proposed changing the conventional “statistical significance” threshold (i.e.,the alpha level) from p ≤ .05 to p ≤ .005 for all novel claims with relatively low prior odds. They provided two arguments for why lowering the significance threshold would “immediately improve the reproducibility of scientific research.” First, a p-value near .05provides weak evidence for the alternative hypothesis. Second, under certain assumptions, an alpha of .05 leads to high false positive report probabilities (FPRP2 ; the probability that a significant finding is a false positive

Justify your alpha

In response to recommendations to redefine statistical significance to p ≤ .005, we propose that researchers should transparently report and justify all choices they make when designing a study, including the alpha level

A demographic interpretation of Grime's triangle

1.The CSR theory of life-history strategies of Grime, and demographically based theories of life history represent strongly contrasting approaches that have yet to be reconciled. 2. It is argued that there are a priori grounds for analogy between Grime's three primary strategies of the established phase in plants and the demographic processes of growth (≈C), survival (≈S), and fecundity (≈R). 3. The contribution of growth, fecundity and survival to the finite rate of population increase λ was calculated for populations of 18 plant species that have also been classified according to Grime's CSR scheme. The match between the demographic classification of species based on these data and their CSR status was determined using a randomization test, and no significant match between the two was found. The reasons for this result are discussed, and it is concluded that it would be premature to abandon attempts to reconcile these two important approaches to plant life history

Graphical models of applicants for credit

Graphical models are a class of statistical tools which have recently undergone extensive theoretical development. They allow one to build models representing the relationships between large numbers of variables, helping to identify paths by which different variables are influenced by others. They look particularly promising for credit-scoring and credit-control problems, since they allow the construction of a holistic applicant model. They can be used in an investigative way, displaying the major influences between variables, or dynamically, allowing statistical prediction of the likely behaviour of individual applicants. They can also be used 'in reverse' to identify the characteristics of individuals demonstrating certain kinds of behaviour. This paper describes an initial investigation into the value of graphical models for bank loans. In particular,we describe the graphical models we constructed for a large set of unsecured personal loan data, and we draw some general conclusions