What do (some of) our association measures measure (most)? Association?

This paper discusses the degree to which some of the most widely-used measures of association in corpus linguistics are not particularly valid in the sense of actually measuring association rather than some amalgam of a lot of frequency and a little association. The paper demonstrates these issues on the basis of hypothetical and actual corpus data and outlines implications of the findings. I then outline how to design an association measure that only measures association and show that its behavior supports the use of the log odds ratio as a true association-only measure but separately from frequency; in addition, this paper sets the stage for an analogous review of dispersion measures in corpus linguistics.

The Predictive Power of Transition Matrices

When working with Markov chains, especially if they are of order greater than one, it is often necessary to evaluate the respective contribution of each lag of the variable under study on the present. This is particularly true when using the Mixture Transition Distribution model to approximate the true fully parameterized Markov chain. Even if it is possible to evaluate each transition matrix using a standard association measure, these measures do not allow taking into account all the available information. Therefore, in this paper, we introduce a new class of so-called "predictive power" measures for transition matrices. These measures address the shortcomings of traditional association measures, so as to allow better estimation of high-order models.

A Test for Multiple Binary Endpoints with Continuous Latent Distribution in Clinical Trials

In clinical trials, two or more binary responses obtained by dichotomizing continuous responses are often employed as multiple primary endpoints. Testing procedures for multiple binary variables with latent distribution have not yet been adequately discussed. Based on the association measure among latent variables, we provide a statistic for testing the superiority of at least one binary endpoint. In addition, we propose a testing procedure with a framework in which the trial efficacy is confirmed only when there is superiority of at least one endpoint and non-inferiority of the remaining endpoints. The performance of the proposed procedure is evaluated through simulations.

On the interpretation of inflated correlation path weights in concentration graphs

Statistical models associated with graphs, called graphical models, have become a popular tool for representing network structures in many modern applications. Relevant features of the model are represented by vertices, edges and other higher order structures. A fundamental structural component of the network is represented by paths, which are a sequence of distinct vertices joined by a sequence of edges. The collection of all the paths joining two vertices provides a full description of the association structure between the corresponding variables. In this context, it has been shown that certain pairwise association measures can be decomposed into a sum of weights associated with each of the paths connecting the two variables. We consider a pairwise measure called an inflated correlation coefficient and investigate the properties of the corresponding path weights. We show that every inflated correlation weight can be factorized into terms, each of which is associated either to a vertex or to an edge of the path. This factorization allows one to gain insight into the role played by a path in the network by highlighting the contribution to the weight of each of the elementary units forming the path. This is of theoretical interest because, by establishing a similarity between the weights and the association measure they decompose, it provides a justification for the use of these weights. Furthermore we show how this factorization can be exploited in the computation of centrality measures and describe their use with an application to the analysis of a dietary pattern.

MIDESP: Mutual Information-Based Detection of Epistatic SNP Pairs for Qualitative and Quantitative Phenotypes

The interactions between SNPs result in a complex interplay with the phenotype, known as epistasis. The knowledge of epistasis is a crucial part of understanding genetic causes of complex traits. However, due to the enormous number of SNP pairs and their complex relationship to the phenotype, identification still remains a challenging problem. Many approaches for the detection of epistasis have been developed using mutual information (MI) as an association measure. However, these methods have mainly been restricted to case–control phenotypes and are therefore of limited applicability for quantitative traits. To overcome this limitation of MI-based methods, here, we present an MI-based novel algorithm, MIDESP, to detect epistasis between SNPs for qualitative as well as quantitative phenotypes. Moreover, by incorporating a dataset-dependent correction technique, we deal with the effect of background associations in a genotypic dataset to separate correct epistatic interaction signals from those of false positive interactions resulting from the effect of single SNP×phenotype associations. To demonstrate the effectiveness of MIDESP, we apply it on two real datasets with qualitative and quantitative phenotypes, respectively. Our results suggest that by eliminating the background associations, MIDESP can identify important genes, which play essential roles for bovine tuberculosis or the egg weight of chickens.

The Effects of Two Association Measures on L2 Collocation Processing

The influence of association measures has been little examined in research on L2 collocation processing. For this reason, the present study replicated Öksüz et al. (2020) experiment on intermediate L2 learners of English to determine whether the association measure mutual information (MI) is a stronger predictor of L2 performance than the Log Dice measure. Twenty-two intermediate Arab learners of English completed a timed acceptability judgment task on the online Gorilla platform. The task included (1) high-frequent collocations (e.g., bad news), (2) low-frequent collocations (e.g., only friend), and (3) non-collocates (e.g., true news, wrong friend) which had differing MI and Log Dice scores. Mixed-effects models were built to analyze the participants’ reaction times to the three conditions. The results showed that the frequency of the collocation (operationalized as item type) and its length significantly influenced reaction times, while both MI and Log Dice scores did not surface as significant predictors. This suggests that intermediate English L2 learners are not sensitive to corpus-based association measures. The results have important implications for L2 teaching and testing and may indicate that it is not worthwhile to determine which collocations to include in the materials based mainly on the strength of the association.

ILEOSCOPY: WHEN ILEAL EVALUATION IS NOT MANDATORY DURING COLONOSCOPY

ABSTRACT BACKGROUND: Ileitis is defined as ileal inflammation, with several etiologies, including inflammatory bowel disease (IBD), and can be evaluated during the colonoscopy exam, but its mandatory evaluation is discussed, because of few diagnosis and procedure time. OBJECTIVE: This study aims to evaluate the correlation of colonoscopic ileitis with the clinical presentation, in order to identify the cases where ileal examination is mandatory. METHODS: A retrospective, cross-sectional study was conducted between 2013 and 2017. The examination report, indications for colonoscopy, and medical records were evaluated in order to identify whether the colonoscopic findings were clinically significant. Patients over 18 years of age who had undergone ileoscopy were included, whereas patients below 18 years of age, those with previous intestinal resections, and repeated examinations of the same patient in the study period were excluded. The estimated association measure was the odds ratio with 95% confidence intervals. P-values <0.05 indicated statistical significance. RESULTS: A total of 3382 cases were included. Among these participants, 64.5% were females and the average age was 56.9±13.1 years (18-89 years). Ileal alterations were observed in 5.3% of the patients, with 2.69% being clinically significant between all patients, and 0.96% excluding those with IBD. There was a positive correlation between the ileitis findings and IBD control examinations and a negative correlation in screening and change in bowel habit indications. Among the indications with ileitis clinically significant, IBD control still had a positive correlation, ‘diarrhea’ and ‘others’ did not show a statistical significance, and all other indications presented a negative correlation for ileal assessment. CONCLUSION: Ileal evaluation in only mandatory in IBD control. When the main colonoscopy objective is detecting colonic neoplasms, ileoscopy is unnecessary.

Intra-language: the study of L2 morpheme productivity as within-item variance

This article suggests a method to appraise L2 morphemes productivity in longitudinal learner data. Traditionally, morpheme productivity is believed to depend on type frequency and on proportion between inflected and uninflected lexemes. However, such measures cannot distinguish between rote-learning and rule-learning of target-like forms. In contrast, the association measure ΔP (delta pi) can quantify the extent to which a morpheme is contingent upon a limited number of lexemes. Decreasing contingency might parallel learners’ increasing awareness of asymmetrical morpheme-lexeme distribution in the input and this might be a cue of developing L2 grammatical competence beyond appearances. The paper presents the rationale and procedure for analyzing within-item variance – or the ‘intra-language’ – and illustrates a case-study concerning the perfective morpheme in L2 Italian.

Introducing the “VALOR” analysis framework for auroral field-aligned current sheets using observations from Swarm Alpha and Charlie

&lt;p&gt;The investigation of auroral field-aligned current (FAC) sheets is crucial in the context of space weather research since they serve as main transmitters of energy and momentum across geospace domains. Different magnetosphere-ionosphere coupling modes are reflected by the FACs&amp;#8217; multiscale nature with spatial scales, i.e., latitudinal extensions, ranging from below 1 km to hundreds of kilometers. The multiscale property can be addressed conveniently using ESA&amp;#8217;s three-spacecraft mission Swarm. According to common practice a linear correlation analysis is performed on lagged and band-pass filtered scalar FAC density estimates from two nearby spacecraft.&lt;/p&gt;&lt;p&gt;We introduce the framework VALOR (Vectorial Association of Linearly Oriented Residua) which generalizes the common approach in two ways. First, VALOR utilizes the full magnetic field vector primarily observed at both spacecraft without filtering. Second, VALOR allows to test statistical association measures other than linear correlation in dependence of both time and along-track spacecraft lag. The method is further refined by considering the current sheet&amp;#8217;s polarization, i.e., the directional preference of the associated magnetic field perturbation, which additionally constrains the sheet&amp;#8217;s orientation.&lt;/p&gt;&lt;p&gt;Here, we apply VALOR to 1 Hz magnetic field observations from Swarm Alpha and Charlie and base the association measure on a vectorial version of the mean squared deviation. By means of a sample auroral oval crossing event we demonstrate that the incorporation of vectorial and polarization information helps to focus the association measure in the time-lag parameter plane leading to a smaller FAC spatial scale estimate. This result seems to hold in a statistical context including over 9000 quasi-perpendicular auroral oval crossings from 2014 to 2020. The fact that the VALOR derived FAC locations reflect the known ellipsoidal shapes of the auroral ovals speaks to the overall plausibility of the method as well as the independently supported finding that large-scale FACs (&gt;300 km) dominate the dawn and dusk sectors while smaller scale FACs gain importance at noon and midnight. Among the various opportunities for future work are an application to 50 Hz high-resolution Swarm data as well as the investigation of the solar controlling parameters.&lt;/p&gt;