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Correlation Statistics (correlation + statistics)
Selected AbstractsAn Independent Evaluation of Four Quantitative Emergency Department Crowding ScalesACADEMIC EMERGENCY MEDICINE, Issue 11 2006Spencer S. Jones MStat Background Emergency department (ED) overcrowding has become a frequent topic of investigation. Despite a significant body of research, there is no standard definition or measurement of ED crowding. Four quantitative scales for ED crowding have been proposed in the literature: the Real-time Emergency Analysis of Demand Indicators (READI), the Emergency Department Work Index (EDWIN), the National Emergency Department Overcrowding Study (NEDOCS) scale, and the Emergency Department Crowding Scale (EDCS). These four scales have yet to be independently evaluated and compared. Objectives The goals of this study were to formally compare four existing quantitative ED crowding scales by measuring their ability to detect instances of perceived ED crowding and to determine whether any of these scales provide a generalizable solution for measuring ED crowding. Methods Data were collected at two-hour intervals over 135 consecutive sampling instances. Physician and nurse agreement was assessed using weighted , statistics. The crowding scales were compared via correlation statistics and their ability to predict perceived instances of ED crowding. Sensitivity, specificity, and positive predictive values were calculated at site-specific cut points and at the recommended thresholds. Results All four of the crowding scales were significantly correlated, but their predictive abilities varied widely. NEDOCS had the highest area under the receiver operating characteristic curve (AROC) (0.92), while EDCS had the lowest (0.64). The recommended thresholds for the crowding scales were rarely exceeded; therefore, the scales were adjusted to site-specific cut points. At a site-specific cut point of 37.19, NEDOCS had the highest sensitivity (0.81), specificity (0.87), and positive predictive value (0.62). Conclusions At the study site, the suggested thresholds of the published crowding scales did not agree with providers' perceptions of ED crowding. Even after adjusting the scales to site-specific thresholds, a relatively low prevalence of ED crowding resulted in unacceptably low positive predictive values for each scale. These results indicate that these crowding scales lack scalability and do not perform as designed in EDs where crowding is not the norm. However, two of the crowding scales, EDWIN and NEDOCS, and one of the READI subscales, bed ratio, yielded good predictive power (AROC >0.80) of perceived ED crowding, suggesting that they could be used effectively after a period of site-specific calibration at EDs where crowding is a frequent occurrence. [source] Graphical analyses of personality disorders in five-factor model spaceEUROPEAN JOURNAL OF PERSONALITY, Issue 4 2005Brian P. O'ConnorArticle first published online: 22 JUN 200 Current knowledge of the associations between personality disorders (PDs) and the five-factor model (FFM) is based largely on the results of linear correlation statistics. Yet we do not know whether FFM,PD associations are indeed linear, and correlational statistics are not directly informative regarding the FFM deviations of individuals with PDs. In this study, graphical analyses of FFM,PD associations for a large, clinical and nonclinical combined sample revealed a diversity of linear and nonlinear FFM patterns, at both the domain and facet levels, for most PDs. However, the FFM deviations from normative levels were only moderate. The discussion focuses on the strengths and weaknesses of the FFM approach to PDs. Copyright © 2005 John Wiley & Sons, Ltd. [source] A novel approach to enable decorrelating multiuser detection without matrix inversion operationsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2004Hsiao-Hwa Chen Abstract This paper proposes a non-matrix inversion based algorithm to implement decorrelating detection (DD), namely quasi-decorrelating detector (QDD), which uses truncated matrix series expansion to overcome the problems associated with the matrix inversion in DD, such as noise enhancement, computational complexity and matrix singularity, etc. Two alternative QDD implementation schemes are presented in this paper; one is to use multi-stage feedforward filters and the other is to use an nth order single matrix filter (neither of which involves matrix inversion). In addition to significantly reduced computational complexity if compared with DD, the QDD algorithm offers a unique flexibility to trade among MAI suppression, near-far resistance and noise enhancement depending on varying system set-ups. The obtained results show that the QDD outperforms DD in either AWGN or multipath channel if a proper number of feed-forward stages can be used. We will also study the impact of correlation statistics of spreading codes on the QDD's performance with the help of a performance-determining factor derived in the paper, which offers a code-selection guideline for the optimal performance of QDD algorithm. Copyright © 2004 John Wiley & Sons, Ltd. [source] Prediction of experimentally unknown re distances of organic molecules from Dunning basis set extrapolations for ab initio post-HF calculationsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2006Alexander Neugebauer Abstract An approach to estimate equilibrium re bond lengths of organic molecules which contain standard bonding situations for CC, CH, CO and CN distances from only one equation is presented. For this, optimizations of molecular geometries using correlated post-Hartree,Fock and density functional methods have been performed. A selection scheme was developed to determine the most reliable methodology for prediction of equilibrium re distances of covalent bonds from a set of investigated theoretical methods. Consequently, distances computed in the CCSD(T) procedure via exponential extrapolation from a consecutive set of Dunning cc-pVXZ basis sets by use of Eqn (2) are accurate up to ±,0.0005,Å in comparison to experimentally available re distances. Applications for predictions of the experimentally unknown re distances of methanol, methylamine and methylenimine are presented. Additionally the estimation of re distances of larger, chemically more interesting molecules is possible by lower order calculations (e.g. DFT B3LYP/cc-pVDZ) via linear correlation statistics using the results from our re reference model system via Eqn (3). Copyright © 2006 John Wiley & Sons, Ltd. [source] Effect of obesity on airway inflammation: a cross-sectional analysis of body mass index and sputum cell countsCLINICAL & EXPERIMENTAL ALLERGY, Issue 7 2007D. C. Todd Summary Background Several observational studies have demonstrated an association between obesity and asthma. Studies evaluating exhaled nitric oxide levels and obesity have revealed that a higher body mass index (BMI) is associated with elevated exhaled nitric oxide levels. Airway inflammation using sputum cell counts has not been assessed in obese patients with airway diseases. Objective The primary aim of this study was to determine whether obesity (based on BMI) is associated with eosinophilic or neutrophilic bronchitis. Methods The results from a database of induced sputum cell counts were compared with BMI and analysed using correlation statistics, regression and parametric and non-parametric analysis. Results Seven-hundred and twenty-seven adult participants with an equal number of sputum samples were included in the analysis. BMI varied from 14.5 to 55 kg/m2. Sputum total cell count (mean±SD: 12.9 × 106 cell/g±21.5), eosinophil percent (median; min to max: 0.3%; 0,89.0), and neutrophil percent (mean±SD: 63.5±26.6%) were within normal limits. Participants with asthma had a higher percentage of sputum eosinophils than those without asthma (P=0.01). However, there was no difference in the total or differential cell counts among the obese and non-obese participants, when the data were analysed according to BMI category, gender, dose of inhaled corticosteroid, and presence or absence of asthma. Conclusion In this large sample of adult asthmatic and non-asthmatic participants, there was no association between BMI and airway inflammation measured by sputum cell counts. Other mechanisms to explain the relationship between obesity and asthma will need to be explored if this association is to be better understood. [source] | ||||||||||