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Important Explanatory Variables (important + explanatory_variable)
Selected AbstractsTrends in NE Atlantic landings (southern Portugal): identifying the relative importance of fisheries and environmental variablesFISHERIES OCEANOGRAPHY, Issue 3 2005KARIM ERZINI Abstract Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south-east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with non-lagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings. [source] Detecting year-of-birth mortality patterns with limited dataJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2008S. J. Richards Summary., Late life mortality patterns are of crucial interest to actuaries assessing risk of longevity, most obviously for annuities and defined benefit pension schemes. The stability of public finances is also affected, as the governments have very substantial risk of longevity in the form of state benefits and public sector pension schemes. One important explanatory variable for late life mortality patterns is year of birth. Previous work has demonstrated various techniques for detecting such patterns, but always with long time series of mortality rates. The paper describes two alternative ways to detect such patterns, even with missing population data or the absence of a time series. The paper finds support for the idea that different birth cohorts have different rates of aging. [source] Some benefits of dichotomization in psychiatric and criminological researchCRIMINAL BEHAVIOUR AND MENTAL HEALTH, Issue 2 2000Professor David P. Farrington PhD FBA Background The product-moment correlation r is widely used in criminology and psychiatry to measure strength of association. However, most criminological and psychiatric variables contravene its underlying assumptions. Aim To compare statistical measures of association based on dichotomous variables with the use of r. Method Explanatory variables for delinquency are investigated in the Pittsburgh Youth Study using a sample of 506 boys aged 13,14. Results Dichotomization does not necessarily cause a decrease in measured strength of associations. Conclusions about the most important explanatory variables for delinquency were not greatly affected by using dichotomous as opposed to continuous variables, by different dichotomization splits, or by using logistic versus OLS multiple regression. Non-linear relationships, interaction effects and multiple risk factor individuals were easily studied using dichotomous data. Conclusions Dichotomization produces meaningful findings that are easily understandable to a wide audience. Measures of association for dichotomous variables, such as the odds ratio, have many advantages and are often more realistic and meaningful measures of strength of relationship than the product-moment correlation r. Copyright © 2000 Whurr Publishers Ltd. [source] Environmental determinants of amphibian and reptile species richness in ChinaECOGRAPHY, Issue 4 2007Hong Qian Understanding the factors that regulate geographical variation in species richness has been one of the fundamental questions in ecology for decades, but our knowledge of the cause of geographical variation in species richness remains poor. This is particularly true for herpetofaunas (including amphibians and reptiles). Here, using correlation and regression analyses, we examine the relationship of herpetofaunal species richness in 245 localities across China with 30 environmental factors, which include nearly all major environmental factors that are considered to explain broad-scale species richness gradients in such theories as ambient energy, water,energy dynamics, productivity, habitat heterogeneity, and climatic stability. We found that the species richness of amphibians and reptiles is moderately to strongly correlated with most of the environmental variables examined, and that the best fit models, which include explanatory variables of temperature, precipitation, net primary productivity, minimum elevation, and range in elevation, explain ca 70% the variance in species richness for both amphibians and reptiles after accounting for sample area. Although water and temperature are important explanatory variables to both amphibians and reptiles, water variables explain more variance in amphibian species richness than in reptile species richness whereas temperature variables explain more variance in reptile species richness than in amphibian species richness, which is consistent with different physiological requirements of the two groups of organisms. [source] Biotic and abiotic influences on the recruitment of male perch in Windermere, U.K.JOURNAL OF FISH BIOLOGY, Issue 6 2004C. G. M. Paxton Perch Perca fluviatilis recruitment (based on the catch per unit effort, CPUE, of 2 or 3 year male perch) varied greatly from 1941 to 1995 in Windermere, U.K., with year class strengths strongly synchronous between the two basins of this temperate, mesotrophic lake. Statistically significant modified Ricker (Saila-Lorda) stock-recruitment curves could be fitted to data from three of four sampling sites, while the presence of widespread disease and late summer water temperature were also important explanatory variables. Multiple-regression analyses revealed no influences of pike Esox lucius recruitment, zooplankton abundance, or the climatic influences (i.e. North Atlantic Oscillation and displacement of the summer position of the Gulf Stream) on perch recruitment over and above associated influences from temperature. Fitted models realistically explained up to c. 60% of the observed variation in perch recruitment. [source] Dental Service Utilization among Urban and Rural Older Adults in China , A Brief CommunicationJOURNAL OF PUBLIC HEALTH DENTISTRY, Issue 3 2007Bei Wu PhD Abstract Objectives: China's health care system is bifurcated in nature between rural and urban areas. In addition, there is a huge gap in socioeconomic status between rural and urban residents. The purpose of the study was to examine the factors related to dental visits among elders in rural and urban areas of Shanghai, China. Methods: Using a stratified random sampling method, a cross-sectional, face-to-face survey was conducted among elders aged 60 years and above in Shanghai during 2003-04. A total of 1,044 older respondents were included in the sample. Results: There was a significant urban and rural difference in dental visit rates over the 12-month period of the study. Results from the logistic regression analysis suggested that residing in urban areas was a significant positive factor related to dental visits. In addition, being younger, being able to pay out-of-pocket medical expenses, having had regular medical checkups, having a higher number of limitations because of chronic conditions, and being more concerned about eating a healthy diet were associated with increased odds of dental visits. Conclusions: Results suggest that urban,rural differences, as reflected in the socioeconomic status gap, disparity in medical insurance coverage, and access to dental care, have a significant impact on the use of dental services by Chinese elders. Individual sociodemographic characteristics, health status, and health attitude are important explanatory variables. [source] | ||||||||||