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Explanatory Variables (explanatory + variable)
Kinds of Explanatory Variables Selected AbstractsExplanatory Variables for per Capita Stocks and Flows of Copper and ZincJOURNAL OF INDUSTRIAL ECOLOGY, Issue 1-2 2006Claudia R. Binder A number of potential explanatory variables for the stocks and flows of copper and zinc in contemporary technological societies are co-analyzed with the tools of exploratory data analysis. A one-year analysis (circa 1994) is performed for 50 countries that comprise essentially all anthropogenic stocks and flows of the two metals. The results show that (1) The key explanatory variable for metal use is gross domestic product (GDP) per capita (purchasing power parity, PPP). By itself, GDP explains between one-third and one-half of the variance of per capita copper and zinc use. Other variables that were significantly correlated with copper and zinc use included stock of passenger cars and television sets (per 1, 000 people); two infrastructure variables, wired telephone connections, urban population, and value added inmanufacturing. The results do not provide evidence supporting the Kuznets curve hypothesis for these metals. (2) Metal use per capita can be estimated using multiple regression equations. For copper, the natural logarithm of use is related to the explanatory variables GDP (PPP), value added in manufacturing, and urban population. This model explains 80% of the variance among the different countries (r2= 0.79). The natural logarithm of zinc use is related to GDP (PPP) and value added in manufacturing with an r2 of 0.75; (3) For both metals, rates of metal fabrication, use, net addition to stock, and discard in low-and high-income countries differ significantly from each other. Our statistical analyses thus provide a basis for estimating the potential development of metal use, net addition to stock, and discard, using data on explanatory variables that are available at the international level. [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] Determinants of continuity and change over 10 years in young women's smokingADDICTION, Issue 3 2009Liane McDermott ABSTRACT Aims To examine prospectively continuity and change in smoking behaviour and associated attributes over a 10-year period. Design, setting and participants Participants (initially aged 18,23 years) in the Australian Longitudinal Study on Women's Health completed postal questionnaires in 1996, 2000, 2003 and 2006. The analysis sample was 6840 women who participated in all surveys and provided complete smoking data. Measurements Outcome variables were transitions in smoking behaviour between surveys 1 and 2, 2 and 3, 3 and 4 and 1 and 4. Attributes that differentiated continuing smokers from quitters, relapsers from ex-smokers and adopters from never smokers were examined for each survey period. Explanatory variables included previous smoking history, demographic, psychosocial, life-style risk behaviour and life-stage transition factors. Findings Over 10 years, 23% of participants either quit, re-started, adopted or experimented with smoking. Recent illicit drug use and risky or high-risk drinking predicted continued smoking, relapse and smoking adoption. Marriage or being in a committed relationship was associated significantly with quitting, remaining an ex-smoker and not adopting smoking. Living in a rural or remote area and lower educational attainment were associated with continued smoking; moderate and high physical activity levels were associated positively with remaining an ex-smoker. Conclusions Life-style and life-stage factors are significant determinants of young women's smoking behaviour. Future research needs to examine the inter-relationships between tobacco, alcohol and illicit drug use, and to identify the determinants of continued smoking among women living in rural and remote areas. Cessation strategies could examine the role of physical activity in relapse prevention. [source] When is Commuting Desirable to the Individual?GROWTH AND CHANGE, Issue 3 2004David T. Ory ABSTRACT Commuting is popularly viewed as a stressful, costly, time-wasting experience from the individual perspective, with the attendant congestion imposing major social costs as well. However, several authors have noted that commuting can also offer benefits to the individual, serving as a valued transition between the home and work realms of personal life. Using survey data collected from about 1,300 commuting workers in three San Francisco Bay Area neighborhoods, empirical models are developed for four key variables measured for commute travel, namely: Objective Mobility, Subjective Mobility, Travel Liking, and Relative Desired Mobility. Explanatory variables include measures of general travel-related attitudes, personality traits, lifestyle priorities, and sociodemographic characteristics. Both descriptive statistics and analytical models indicate that commuting is not the unmitigated burden that it is widely perceived to be. About half of the sample were relatively satisfied with the amount they commute, with a small segment actually wanting to increase that amount. Both the psychological impact of commuting, and the amounts people want to commute relative to what they are doing now, are strongly influenced by their liking for commuting. An implication for policy is that some people may be more resistant than expected toward approaches intended to induce reductions in commuting (including, for example, telecommuting). New creativity may be needed to devise policies that recognize the inherent positive utility of travel, while trying to find socially beneficial ways to fulfill desires to maintain or increase travel. [source] Risk adjusted resource utilization for AMI patients treated in Japanese hospitalsHEALTH ECONOMICS, Issue 4 2007Edward Evans Abstract Though risk adjustment is necessary in order to make equitable comparisons of resource utilization in the treatment of acute myocardial infarction patients, there is little in the literature that can be practically applied without access to clinical records or specialized registries. The aim of this study is to show that effective models of resource utilization can be developed based on administrative data, and to demonstrate a practical application of the same models by comparing the risk-adjusted performance of the hospitals in our dataset. The study sample included 1748 AMI cases discharged from 10 large, private teaching hospitals in Japan, between 10 April 2001 and 30 June 2004. Explanatory variables included procedures (CABG and PCI), length of stay, outcome, patient demographics, diagnosis and comorbidity status. Multiple linear regression models constructed for the study were able to account for 66.5, 27.7, and 58.4% of observed variation in total charges, length of stay and charges per day, respectively. The performance of models constructed for this study was comparable to or better than performance reported by other studies that made use of explanatory variables extracted from clinical data. The use of administrative data in risk adjustment makes broad scale application of risk adjustment feasible. Copyright © 2006 John Wiley & Sons, Ltd. [source] Nurse absenteeism and workload: negative effect on restraint use, incident reports and mortalityJOURNAL OF ADVANCED NURSING, Issue 6 2007Lynn Unruh Abstract Title.,Nurse absenteeism and workload: negative effect on restraint use, incident reports and mortality Aim., This paper is a report of a study to assess the impact of nurse absenteeism on the quality of patient care. Background., Nurse absenteeism is a growing management concern. It can contribute to understaffed units, staffing instability, and other factors that could have a negative impact on patient care. The impacts of absenteeism on the quality of nursing care have rarely been studied. Method., Retrospective monthly data from incident reports and staffing records in six inpatient units for 2004 were analysed. Dependent variables were the numbers of restraints, alternatives to restraints, incident reports, deaths, and length of stay. Explanatory variables were nurse absenteeism hours, patient days per nursing staff, and interaction between these variables. Controls were patient acuity and unit characteristics. Fixed effects regressions were analysed as regular or negative binomial models. Findings., Neither high Registered Nurse absenteeism nor high patient load was related to restraint use when taken separately. However, high Registered Nurse absenteeism was related to restraint use when patient load was high. Registered Nurse absenteeism was related to a lower use of alternatives to restraints. Incident reports were increased by high patient load, but not absenteeism, or absenteeism given patient load. When both patient load and absenteeism were high, deaths were higher also. Conclusion., Absenteeism alone may not be a strong factor in lowering quality, but the combination of high Registered Nurse absenteeism and high patient load could be a factor. Staffing and absenteeism may be part of a vicious cycle in which low staffing contributes to unit absenteeism, which contributes to low staffing, and so on. [source] Bonus-Malus Scales in Segmented Tariffs With Stochastic Migration Between SegmentsJOURNAL OF RISK AND INSURANCE, Issue 4 2003Natacha Brouhns This article proposes a computer-intensive methodology to build bonus-malus scales in automobile insurance. The claim frequency model is taken from Pinquet, Guillén, and Bolancé (2001). It accounts for overdispersion, heteroskedasticity, and dependence among repeated observations. Explanatory variables are taken into account in the determination of the relativities, yielding an integrated automobile ratemaking scheme. In that respect, it complements the study of Taylor (1997). [source] The influence of multi-scale environmental variables on the distribution of terricolous lichens in a fog desertJOURNAL OF VEGETATION SCIENCE, Issue 6 2006Jennifer S. Lalley Abstract Question: How do environmental variables in a hyper-arid fog desert influence the distribution patterns of terricolous lichens on both macro- and micro-scales? Location: Namib Desert, Namibia. Methods: Sites with varying lichen species cover were sampled for environmental variables on a macro-scale (elevation, slope degree, aspect, proximity to river channels, and fog deposition) and on a micro-scale (soil structure and chemistry). Macro-scale and micro-scale variables were analysed separately for associations with lichen species cover using constrained ordination (DCCA) and unconstrained ordination (DCA). Explanatory variables that dominated the first two axes of the constrained ordinations were tested against a lichen cover gradient. Results: Elevation and proximity to river channels were the most significant drivers of lichen species cover in the macro-scale DCCA, but results of the DCA suggest that a considerable percentage of variation in lichen species cover is unexplained by these variables. On a micro-scale, sediment particle size explained a majority of lichen community variations, followed by soil pH. When both macro and micro-scale variables were tested along a lichen cover gradient, soil pH was the only variable to show a significant relationship to lichen cover. Conclusion: The findings suggest that landscape variables contribute to variations in lichen species cover, but that stronger links occur between lichen growth and small-scale variations in soil characteristics, supporting the need for multi-scale approaches in the management of threatened biological soil crust communities and related ecosystem functions. [source] Determinants of Antenatal Care Utilization in Three Rural Areas of VietnamPUBLIC HEALTH NURSING, Issue 4 2007Lieu Thi Thuy Trinh ABSTRACT Objective: To identify factors associated with any use of antenatal care (ANC), gestational age at entry to ANC, number of visits, and overall ANC utilization in the three provinces of Long an, Ben tre, and Quang ngai. Data: The Vietnam-Australia Primary Health Care Project conducted cross-sectional surveys in 1998,1999. Data from 1,335 eligible women were available for analysis. Methods: Explanatory variables were selected using the Andersen Health Seeking Behavior Model and analyzed using multivariate regression techniques. Results: External environment, predisposing characteristics, and need, which existed before contact with ANC providers, were most related to using any ANC and gestational age at entry to ANC. However, ANC services provided to women and personal health care during pregnancy, which could have resulted from initial contact with ANC providers, were most related to continuation of ANC visits and overall ANC utilization. Significant variability in the use of ANC existed between provinces and between subsets of women in each province. Conclusion: To have more women who attend ANC and attend early, promotion should be targeted at high-risk groups of women. However, to improve the number of ANC visits and overall utilization, the quality of ANC services should be improved. [source] Parents underestimate their child`s overweightACTA PAEDIATRICA, Issue 9 2010Nina Vuorela Abstract Aim:, The aim of this study was to evaluate parents' ability to perceive the weight status of their children. Methods:, This cross-sectional study was performed on 5 (n = 310) and 11-year-old (n = 296) children. The height, weight and waist circumference were measured. Body mass index (BMI, kg/m²) was calculated. The International Obesity Task Force criteria and the British cut-off points were used to classify BMI and waist circumference. Parents filled out a questionnaire concerning their perception of the weight class of their child. The parents and the 11-year-old children estimated their own weight class. For analysis, the measured and perceived weight classes were divided into two categories; normal weight (including underweight) and overweight or obese. To measure the agreement cross-tabulation with Cohen's Kappa was used. Explanatory variables associated with misclassification of overweight children as normal weight were examined by logistic regression modelling. Results:, The prevalence of overweight (including obese) was 17.4% and 21.6% in 5- and 11-year-old children in this study. Only a few parents misclassified their normal weight children as overweight. By contrast, a majority of parents to the 5-year-old children and about half of the parents to the 11-year-old children misclassified them as normal weight. Using waist circumference for body size classification did not improve parents' performance. Mothers performed best when estimating own weight class. Conclusion:, A majority of parents fail to recognize overweight or obesity in their 5- and 11-year-old children. The underestimation of overweight may impair the motivation of the parents to adopt weight control. [source] Exploring the Frontier of Livelihoods ResearchDEVELOPMENT AND CHANGE, Issue 1 2005Leo De Haan This article discusses the value of livelihoods studies and examines the obstacles which have prevented it from making a greater contribution to understanding the lives of poor people over the past decade. After examining the roots of the livelihoods approach, two major challenges are explored: the conceptualization of the problem of access, and how to achieve a better understanding of the mutual link between livelihood opportunities and decision-making. The article concludes that access to livelihood opportunities is governed by social relations, institutions and organizations, and that power is an important (and sometimes overlooked) explanatory variable. In discussing the issue of access to livelihood opportunities, the authors note the occurrence of both strategic and unintentional behaviour and the importance of structural factors; they discuss concepts of styles and pathways, which try to cater for structural components and regularities; and they propose livelihood trajectories as an appropriate methodology for examining these issues. In this way, the article also sets the agenda for future livelihoods research. [source] Ethnic differences in the timely diagnosis of children with Type 1 diabetes mellitus in the Netherlands: clinical presentation at onsetDIABETIC MEDICINE, Issue 3 2007J. J. N. Van Laar Abstract Aims Little is known about ethnic differences in the timely diagnosis of Type 1 diabetes mellitus (Type 1 DM). This study aimed to assess ethnic inequalities in the timely diagnosis of Type 1 DM, as indicated by a more adverse clinical condition at onset. In addition, we assessed whether these differences could be explained by differences in socio-economic status. Methods From a national register, we selected 3128 children aged < 15 years with newly diagnosed Type 1 DM. Ethnic differences in serum glucose, blood pH, bicarbonate, presence of ketonuria, level of consciousness, hydration status, and diabetic ketoacidosis were assessed by logistic regression. A measure of socio-economic status based on postal codes was used as an explanatory variable. Results The risk of adverse clinical presentation was 1.5,2 times higher in non-Western immigrants than Dutch children, while Western immigrant children did not differ from Dutch children. Blood pH, bicarbonate level, and level of consciousness were lower in Turkish and Antillean children in particular. The adverse socio-economic position of immigrant children contributed very little to these differences in clinical presentation. Conclusions Non-Western children were likely to be sicker at first presentation of Type 1 DM, and thus diagnosis may have been delayed. These disparities were not accounted for by differences in socio-economic status. Possible explanations may be difficulties in recognition of symptoms, failure of GPs to take symptom reporting seriously and lack of awareness of the fact that Type 1 DM occurs more often in certain ethnic groups. [source] Species,area relationships of red-listed species in old boreal forests: a large-scale data analysisDIVERSITY AND DISTRIBUTIONS, Issue 5 2009Olli-Pekka Tikkanen Abstract Aim, Species,area relationships are often applied, but not generally approved, to guide practical conservation planning. The specific species group analysed may affect their applicability. We asked if species,area curves constructed from extensive databases of various sectors of natural resource administration can provide insights into large-scale conservation of boreal forest biodiversity if the analyses are restricted only to red-listed species. Location, Finland, northern Europe. Methods, Our data included 12,645 records of 219 red-listed Coleoptera and Fungi from the whole of Finland. The forest data also covered the entire country, 202,761 km2. The units of species,area analyses were 224 municipalities where the red-listed forest species have been observed. We performed a hierarchical partitioning analysis to reveal the relative importance of different potential explanatory variables. Based on the results, for all red-listed species, species associated with coniferous trees and for Fungi, the area of economically over-aged forests explained the best the variation in data. For species associated with deciduous trees and Coleoptera, the forest area explained better variation in data than the area of old forests. In the subsequent log,log species,area regression analyses, we used the best variables as the explanatory variable for each species group. Results, There was a strong relationship between the number of all red-listed species and the area of old forests remaining, with a z -value of 0.45. The area explained better the number of species associated with conifer trees and Fungi than the number of species associated with deciduous trees and Coleoptera. Main conclusions, The high z -values of species,area curves indicate that the remaining old-growth patches constitute a real archipelago for the conifer-associated red-listed species, since lower values had been expected if the surrounding habitat matrix were a suitable habitat for the species analysed. [source] Cross Section and Panel Data Estimators for Nonseparable Models with Endogenous RegressorsECONOMETRICA, Issue 4 2005Joseph G. Altonji We propose two new methods for estimating models with nonseparable errors and endogenous regressors. The first method estimates a local average response. One estimates the response of the conditional mean of the dependent variable to a change in the explanatory variable while conditioning on an external variable and then undoes the conditioning. The second method estimates the nonseparable function and the joint distribution of the observable and unobservable explanatory variables. An external variable is used to impose an equality restriction, at two points of support, on the conditional distribution of the unobservable random term given the regressor and the external variable. Our methods apply to cross sections, but our lead examples involve panel data cases in which the choice of the external variable is guided by the assumption that the distribution of the unobservable variables is exchangeable in the values of the endogenous variable for members of a group. [source] Cadmium uptake by earthworms as related to the availability in the soil and the intestineENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Leonard A. Oste Abstract The free metal concentration in the soil solution is often considered a key parameter for metal uptake by and toxicity to soft-bodied soil organisms. The equilibrium partitioning theory, which assumes a relationship between the contaminant concentration in pore water and the contaminant concentration in the body tissue, can be used to describe uptake by earthworms. This theory has proved useful for organic chemicals, but its applicability is less clear for metals. In this study, the Cd concentration in soil pore water (pw) was varied by increasing the soil pH by the addition of lime (Ca(OH)2) and by adding manganese oxide (MnO2), which has a high metal binding capacity. Both lime (0.135% w/w) and MnO2 (1% w/w) decreased [Cd2+]pw by a factor of 25, while CdWorm was reduced only by a factor of 1.3 in lime-treated soils and 2.5 in MnO2 -treated soils. Cadmium uptake was weakly related to the free metal concentration (R2adj = 0.66). Adding pH as an explanatory variable increased R2adj to 0.89, indicating that Cd uptake from pore water is pH dependent, which might be attributed to competition of protons and Cd at the surface of the earthworm body. However, previous earthworm experiments in reconstituted groundwater showed a conspicuously smaller pH dependency of Cd uptake. The differences in metal uptake between earthworms in lime- and MnO2 -treated soils are therefore more likely to reflect the predominance of pH-independent intestinal uptake of Cd. Equilibrating the soil with a solution of 0.01 M CaCl2 and 0.1 M triethanolamine (buffered at pH 7.2), simulating the conditions prevailing in the worm intestine, yielded free Cd concentrations that were closely (R2adj = 0.83) and linearly related to the Cd concentration in the earthworm tissue. [source] Soil solution concentration of Cd and Zn canbe predicted with a CaCl2 soil extractEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2003F. Degryse Summary Risk assessment of heavy metals in soil requires an estimate of the concentrations in the soil solution. In spite of the numerous studies on the distribution of Cd and Zn in soil, few measurements of the distribution coefficient in situ, Kd, have been reported. We determined the Kd of soils contaminated with Cd and Zn by measuring metal concentrations in the soil and in the soil solution and attempted to predict them from other soil variables by regression. Soil pH explained most of the variation in logKd (R2 = 0.55 for Cd and 0.70 for Zn). Introducing organic carbon content or cation exchange capacity (CEC) as second explanatory variable improved the prediction (R2 = 0.67 for Cd and 0.72 for Zn), but these regression models, however, left more than a factor of 10 of uncertainty in the predicted Kd. This large degree of uncertainty may partly be due to the variable degree of metal fixation in contaminated soils. The labile metal content was measured by isotopic dilution (E value). The E value ranged from 18 to 92% of the total metal content for Cd and from 5 to 68% for Zn. The prediction of Kd improved when metals in solution were assumed to be in equilibrium with the labile metal pool instead of the total metal pool. It seems necessary therefore to discriminate between ,labile' and ,fixed' pools to predict Kd for Cd and Zn in field contaminated soils accurately. Dilute salt extracts (e.g. 0.01 m CaCl2) can mimic soil solution and are unlikely to extract metals from the fixed pool. Concentrations of Cd and Zn in the soil solution were predicted from the concentrations of Cd and Zn in a 0.01 m CaCl2 extract. These predictions were better correlated with the observations for field contaminated soils than the predictions based on the regression equations relating logKd to soil properties (pH, CEC and organic C). [source] Testing hypotheses about fecundity, body size and maternal condition in fishesFISH AND FISHERIES, Issue 2 2004Marten A. Koops Abstract Recent research suggests that maternal condition positively influences the number of eggs spawned in fishes. These studies commonly choose a priori to use body length rather than weight as an explanatory variable of offspring production, even though weight is usually the better predictor of fecundity. We are concerned that consistent exclusion of body weight as a predictor of egg production inflates the variance in fecundity attributable to maternal condition. By analysing data on three populations of Atlantic cod (Gadus morhua, Gadidae) and 10 populations of brook trout (Salvelinus fontinalis, Salmonidae), we illustrate the need for a statistically defensible method of model selection to distinguish the effects of maternal condition on egg production from the effects of body size alone. Forward stepwise regression and null model analyses reveal how length-based regressions can significantly over-estimate correlations between condition and fecundity, leading us to conclude that the effect of condition on egg productivity may not be as ubiquitous or as biologically important as previously thought. Our work underscores the need for greater statistical clarity in analyses of the effects of maternal condition on reproductive productivity in fishes. [source] Trends 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] Time to include time to death?HEALTH ECONOMICS, Issue 4 2004The future of health care expenditure predictions Abstract Government projections of future health care expenditures , a great concern given the aging baby-boom generation , are based on econometric regressions that control explicitly for age but do not control for end-of-life expenditures. Because expenditures increase dramatically on average at the end of life, predictions of future cost distributions based on regressions that omit time to death as an explanatory variable will be biased upward (or, more explicitly, the coefficients on age will be biased upward) if technology or other social factors continue to prolong life. Although health care expenditure predictions for a current sample will not be biased, predictions for future cohorts with greater longevity will be biased upwards, and the magnitude of the bias will increase as the expected longevity increases. We explore the empirical implications of incorporating time to death in longitudinal models of health expenditures for the purpose of predicting future expenditures. Predictions from a simple model that excludes time to death and uses current life tables are 9% higher than from an expanded model controlling for time to death. The bias increases to 15% when using projected life tables for 2020. The predicted differences between the models are sufficient to justify reassessment of the value of inclusion of time to death in models for predicting health care expenditures. Copyright © 2003 John Wiley & Sons, Ltd. [source] Contextual Determinants of Reward Systems' Success: An Exploratory StudyHUMAN RESOURCE MANAGEMENT, Issue 3 2001Charles H. Fay Data were collected on successful and unsuccessful reward initiatives. The initiatives included new and modified base pay, short- and long-term incentive, benefits, and perquisite/lifestyle rewards. Initiative success was measured on seven factors, and ten conditions were measured for initiative success. Follow-up telephone calls to most respondents provided more detail for examples. Analysis suggests that a common set of criteria can be used to judge the success of different kinds of programs. Surprisingly, success in plan design was not a significant explanatory variable in reaching success on any criterion of rewards initiative success. © 2001 John Wiley & Sons, Inc. [source] Improving interpolation of daily precipitation for hydrologic modelling: spatial patterns of preferred interpolatorsHYDROLOGICAL PROCESSES, Issue 23 2009Daniel Kurtzman Abstract Detailed hydrologic models require high-resolution spatial and temporal data. This study aims at improving the spatial interpolation of daily precipitation for hydrologic models. Different parameterizations of (1) inverse distance weighted (IDW) interpolation and (2) A local weighted regression (LWR) method in which elevation is the explanatory variable and distance, elevation difference and aspect difference are weighting factors, were tested at a hilly setting in the eastern Mediterranean, using 16 years of daily data. The preferred IDW interpolation was better than the preferred LWR scheme in 27 out of 31 validation gauges (VGs) according to a criteria aimed at minimizing the absolute bias and the mean absolute error (MAE) of estimations. The choice of the IDW exponent was found to be more important than the choice of whether or not to use elevation as explanatory data in most cases. The rank of preferred interpolators in a specific VG was found to be a stable local characteristic if a sufficient number of rainy days are averaged. A spatial pattern of the preferred IDW exponents was revealed. Large exponents (3) were more effective closer to the coast line whereas small exponents (1) were more effective closer to the mountain crest. This spatial variability is consistent with previous studies that showed smaller correlation distances of daily precipitation closer to the Mediterranean coast than at the hills, attributed mainly to relatively warm sea-surface temperature resulting in more cellular convection coastward. These results suggest that spatially variable, physically based parameterization of the distance weighting function can improve the spatial interpolation of daily precipitation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Social capital and children's wellbeing: a critical synthesis of the international social capital literatureINTERNATIONAL JOURNAL OF SOCIAL WELFARE, Issue 1 2006Kristin M. FergusonArticle first published online: 13 JAN 200 Drawing on social capital literature from the international realm, this article presents a critical synthesis of this social resource in relation to children's and youth's wellbeing. Although considerable evidence indicates that social capital can have a positive impact on future outcomes for children and youth, no prior comprehensive review exists of the literature on social capital and children's wellbeing. Adopting the systematic review method (SR), the author explores how social capital has been conceptualised and operationalised as an explanatory variable in research on individual and collective wellbeing with children and youth. Oft-cited indicators of family social capital and community social capital are identified, together with common control variables, such as human and financial capital. The author concludes by examining several social capital trends in relation to children's wellbeing and offering recommendations for future research using a social capital theoretical framework to explore additional outcomes related to children's and youth's wellbeing. [source] Spatial planning, mobilities and culture,Chinese and New Zealand student preferences for Californian travelINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 3 2007Chris Ryan Abstract Itineraries are under-researched within tourism, which is arguably strange given their potential importance as determinants of visitor expenditure distribution, and how itinerary planning may become a tool of destination management in determining which areas are most affected by visitor flows, whether positively or negatively. This exploratory study required students in New Zealand and the Peoples' Republic of China to draw maps of potential trips to the south-west of the USA in order to assess to what degree differences might exist as to (i) preferred places to visit; (ii) durations of stay; (iii) speeds of dispersion and concentration at the points of embarkation and disembarkation (in this instance Los Angeles); and (iv) total distances travelled. Differences were indeed found, and ethnicity appeared to be the main explanatory variable for the differences. Chinese students were found to travel slightly less, not to become so dispersed overall, but were also found to have higher rates of dispersion and slower rates of concentration at the commencement and at the end of the trip. The itineraries also suggest a further triangular pattern of travel that can be added to the categories identified by Oppermann. Copyright © 2007 John Wiley & Sons, Ltd. [source] Autoregressive conditional heteroscedasticity in commodity spot pricesJOURNAL OF APPLIED ECONOMETRICS, Issue 2 2001Stacie Beck Muth's (1961) rational expectations model of commodity markets implies that inventory carryover creates ARCH processes in prices. The model also indicates that the expected price variance is an explanatory variable in price regressions. Hypotheses were tested on price data of twenty commodities using a variation of Engle et al. (1987) ARCH,M technique. An ARCH process was found in storable and not in non-storable commodity data, as expected. However, changes in expected price variance have no significant impact on price. Copyright © 2001 John Wiley & Sons, Ltd. [source] Sorting grid trials to improve size selectivity of red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis) in Turkish bottom trawl fisheryJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2008C. Ayd Summary Sorting grids with two different bar spacings (12 mm and 14 mm) were tested to improve size selectivity of the commercially important fish species, red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis), in Turkish bottom trawl fishery. Fishing trials were carried out with R/V ,Egesüf' between April and May 2003 in Izmir Bay, Aegean Sea, using a traditional bottom trawl. Selectivity data were collected by the top cover method and analyzed by means of a logistic equation with the maximum likelihood method. Selectivity parameters for individual hauls were obtained with the software program cc 2000. Mean selectivity was also estimated and compared using the EC Model software that takes between-haul variations into account. The codend catch size as an additional explanatory variable was used in the comparison. The Kolmogorov,Smirnov (K,S) test was also applied to detect differences between length-frequency distributions in the upper and lower bags of the 12 and 14 mm bar spacings for red mullet and annular sea bream. The mean L50 values of red mullet were 8.7 and 10.0 cm with the 12 and 14 mm grids, respectively. The L50 value of 14 mm was comparable with the L50 value of the codend mesh size; however, the 12 mm value was rather low. The mean L50 values of 12 and 14 mm bar spacings were 8.8 and 10.4 cm for annular sea bream, respectively; the value of 14 mm bar spacing was very close to 50% size at sexual maturity of the species (10.5 cm). The K,S test indicated length distributions of red mullet and annular sea bream in the 12 and 14 mm upper and lower bags as significantly different (P < 0.05). These results show that improving the size selectivity in a multi-species fishery using a single selective device is rather difficult. However, higher size selectivity can be obtained when considering the minimum landing size or the 50% sexual maturity size for a given species. [source] The association of metabolic syndrome with periodontal disease is confounded by age and smoking in a Korean population: the Shiwha,Banwol Environmental Health StudyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2010Dong-Hun Han Han D-H, Lim S-Y, Sun B-C, Paek D, Kim H-D. The association of metabolic syndrome with periodontal disease is confounded by age and smoking in a Korean population: the Shiwha,Banwol Environmental Health Study. J Clin Periodontol 2010; 37: 609,616. doi: 10.1111/j.1600-051X.2010.01580.x. Abstract Aim: Because metabolic syndrome (MS) is pro-inflammatory and periodontitis is inflammatory, we issued the hypothesis that MS (the explanatory variable) is associated with periodontitis (the outcome variable). This study aimed to examine the link between MS and periodontitis among Koreans. Materials and Methods: From the Shiwha,Banwol Environmental Health Study, 1046 subjects aged 18 years or older were cross-sectionally surveyed. All participants underwent comprehensive dental and medical health examinations. The community periodontal index was used to assess periodontitis. Age, gender, monthly family income, smoking, drinking, frequency of daily teeth brushing, and physical activity were evaluated as confounders. Results: MS was strongly associated with periodontitis [odds ratio (OR): 1.7, 95% confidence interval (CI): 1.22,2.37], and MS with more components had a higher association. The association was higher for elders aged 65 years or more, males, and smokers. MS including both high glucose and hypertension had a higher association with the OR of 2.19 (95% CI: 1.23,3.90) comparing with other types of MS. Conclusions: Our results suggested that MS might be associated with periodontitis and the association was confounded by age, gender, and smoking. MS with high glucose and hypertension showed the higher impact on this link. [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] Assessing interaction effects in linear measurement error modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2005Li-Shan Huang Summary., In a linear model, the effect of a continuous explanatory variable may vary across groups defined by a categorical variable, and the variable itself may be subject to measurement error. This suggests a linear measurement error model with slope-by-factor interactions. The variables that are defined by such interactions are neither continuous nor discrete, and hence it is not immediately clear how to fit linear measurement error models when interactions are present. This paper gives a corollary of a theorem of Fuller for the situation of correcting measurement errors in a linear model with slope-by-factor interactions. In particular, the error-corrected estimate of the coefficients and its asymptotic variance matrix are given in a more easily assessable form. Simulation results confirm the asymptotic normality of the coefficients in finite sample cases. We apply the results to data from the Seychelles Child Development Study at age 66 months, assessing the effects of exposure to mercury through consumption of fish on child development for females and males for both prenatal and post-natal exposure. [source] Species interaction and response to wind speed alter the impact of projected temperature change in a montane ecosystemJOURNAL OF VEGETATION SCIENCE, Issue 4 2010Dafydd Crabtree Abstract Question: How does an improved understanding of species interactions, combined with an additional ecological variable (wind speed), alter the projected vegetation response to variation in altitudinal temperature? Location: Cairngorm Mountains, Scotland. Methods: Montane heathland vegetation was sampled from 144 plots (432 quadrats) comprising eight altitudinal transects. Ordination by partial DCA and path analysis was used to confirm: (1) the effect of wind speed and altitude (, temperature) on vegetation structure, i.e. canopy height and cover of bare ground, and (2) the control of arctic/alpine macrolichen occurrence by vegetation structure. Nested regression analysis was used to project the response of vegetation structure and lichen occurrence to temperature change scenarios with and without a step-wise change in future wind speed. Results: Warming trends shifted vegetation zones upwards, with a subsequent loss of suitable habitat for arctic/alpine lichens. However, incorporating wind speed as an additional explanatory variable had an important modifying effect on the vegetation response to temperature: decreasing wind speed exaggerates the effects of increased temperature and vice versa. Our models suggest that for the wind-driven heath examined, a 20% increase in mean wind speed may negate the effect of increased temperature on vegetation structure, resulting in no net change in lichen occurrence. Conclusions: We caution that an improved understanding of species interactions in vegetation response models may force the consideration of locally variable environmental parameters (e.g. wind speed), bringing into question the predicted vegetation response based on standard projections of temperature change along altitudinal gradients. [source] Effects of radio-collars on European badgers (Meles meles)JOURNAL OF ZOOLOGY, Issue 1 2002F. A. M. Tuyttens Abstract The relationships between radio-collaring/tracking and 12 biometric parameters in a population of badgers (Meles meles) that were live-trapped in south-west England were investigated. The length of time for which a badger had worn a radio-collar was selected as an explanatory variable in generalized linear models of three biometric parameters (body condition, body weight and testes volume) irrespective of whether or not age class was included as a variable in the analyses. There was evidence that badgers that had been carrying a radio-collar for 1,100 days had lower body condition scores both when compared to badgers that had not been collared and with those that had been collared for longer than 100 days, suggesting a post-collaring acclimation period. In addition, the time period between first and last capture was longer for radio-collared than non-collared badgers. It is unlikely that this was due to an effect of collaring on trappability or to non-random selection of badgers for collaring. Although testes size differed between non-collared badgers and badgers that had been tagged for > 100 days, the relationship between radio-collaring and reproductive output remained unproven. These results highlight not only the need to assess the welfare aspects of radio-collaring but also the potential intricacy of corollaries of collaring. Explorations such as that reported here are important to the validity of studies that make use of radio-telemetry. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||