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Single Predictor (single + predictor)
Kinds of Single Predictor Selected AbstractsNear-Term Travel Speed Prediction Utilizing Hilbert,Huang TransformCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2009Khaled Hamad In this study, we propose an innovative methodology for such prediction. Because of the inherently direct derivation of travel time from speed data, the study was limited to the use of speed only as a single predictor. The proposed method is a hybrid one that combines the use of the empirical mode decomposition (EMD) and a multilayer feedforward neural network with backpropagation. The EMD is the key part of the Hilbert,Huang transform, which is a newly developed method at NASA for the analysis of nonstationary, nonlinear time series. The rationale for using the EMD is that because of the highly nonlinear and nonstationary nature of link speed series, by decomposing the time series into its basic components, more accurate forecasts would be obtained. We demonstrated the effectiveness of the proposed method by applying it to real-life loop detector data obtained from I-66 in Fairfax, Virginia. The prediction performance of the proposed method was found to be superior to previous forecasting techniques. Rigorous testing of the distribution of prediction errors revealed that the model produced unbiased predictions of speeds. The superiority of the proposed model was also verified during peak periods, midday, and night. In general, the method was accurate, computationally efficient, easy to implement in a field environment, and applicable to forecasting other traffic parameters. [source] Influence of settlement time, human population, park shape and age, visitation and roads on the number of alien plant species in protected areas in the USADIVERSITY AND DISTRIBUTIONS, Issue 6 2002Michael L. McKinney Abstract. I examined a data set of 77 protected areas in the USA (including national and state parks) to determine which of the following variables most strongly influence alien plant species richness: park area, climate (temperature and precipitation), native species richness, visitation rate, local human population size, total road length, park shape and duration of European settlement. Many of these predictor variables are intercorrelated, so I used multiple regression to help separate their effects. In support of previous studies, native species richness was the best single predictor of alien species richness, probably because it was a good estimator of both park area and habitat diversity available for establishment of alien species. Other significant predictors of alien species richness were years of occupation of the area by European settlers and the human population size of adjacent counties. Climate, visitation rate, road length and park shape did not influence alien species richness. The proportion of alien species (alien richness/native richness) is inversely related to park area, in agreement with a previous study. By identifying which variables are most important in determining alien species richness, such findings suggest ways to reduce alien species establishment. [source] Statistical downscaling model based on canonical correlation analysis for winter extreme precipitation events in the Emilia-Romagna regionINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2008A. Busuioc Abstract Optimum statistical downscaling models for three winter precipitation indices in the Emilia-Romagna region, especially related to extreme events, were investigated. For this purpose, the indices referring to the number of events exceeding the long-term 90 percentile of rainy days, simple daily intensity and maximum number of consecutive dry days were calculated as spatial averages over homogeneous sub-regions identified by the cluster analysis. The statistical downscaling model (SDM) based on the canonical correlation analysis (CCA) was used as downscaling procedure. The CCA was also used to understand the large-/regional-scale mechanisms controlling precipitation variability across the analysed area, especially with respect to extreme events. The dynamic (mean sea-level pressure-SLP) and thermodynamic (potential instability-,Q and specific humidity-SH) variables were considered as predictors (either individually or together). The large-scale SLP can be considered a good predictor for all sub-regions in the dry index case and for two sub-regions in the case of the other two indices, showing the importance of dynamical forcing in these cases. Potential instability is the best predictor for the highest mountain region in the case of heavy rainfall frequency, when it can be considered as a single predictor. The combination of dynamic and thermodynamic predictors improves the SDM's skill for all sub-regions in the dry index case and for some sub-regions in the simple daily intensity index case. The selected SDMs are stable in time only in terms of correlation coefficient for all sub-regions for which they are skilful and only for some sub-regions in terms of explained variance. The reasons are linked to the changes in the atmospheric circulation patterns influencing the local rainfall variability in Emilia-Romagna as well as the differences in temporal variability over some sub-regions and sub-intervals. It was concluded that the average skill over an ensemble of the most skilful and stable SDMs for each region/sub-interval gives more consistent results. Copyright © 2007 Royal Meteorological Society [source] Breeding birds on small islands: island biogeography or optimal foraging?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006GARETH J. RUSSELL Summary 1We test MacArthur and Wilson's theory about the biogeography of communities on isolated habitat patches using bird breeding records from 16 small islands off the coasts of Britain and Ireland. 2A traditional examination of patterns of species richness on these islands suggests that area and habitat diversity are important predictors, but that isolation and latitude have a negligible impact in this system. 3Unlike traditional studies, we directly examine the fundamental processes of colonization and local extinction (cessation of breeding), rather than higher-order phenomena such as species richness. 4We find that many of MacArthur and Wilson's predictions hold: colonization probability is lower on more isolated islands, and extinction probability is lower on larger islands and those with a greater diversity of habitats. 5We also find an unexpected pattern: extinction probability is much lower on more isolated islands. This is the strongest relationship in these data, and isolation is the best single predictor of colonization and extinction. 6Our results show that examination of species richness alone is misleading. Isolation has a strong effect on both of the dynamic processes that underlie richness, and in this system, the reductions in both colonization and extinction probability seen on more distant islands have opposing influences on species richness, and largely cancel each other out. 7We suggest that an appropriate model for this system might be optimal foraging theory, which predicts that organisms will stay longer in a resource patch if the distance to a neighbouring patch is large. If nest sites and food are the resources in this system, then optimal foraging theory predicts the pattern we observe. 8We advance the hypothesis that there is a class of spatial systems, defined by their scale and by the taxon under consideration, at which decision-making processes are a key driver of the spatiotemporal dynamics. The appropriate theory for such systems will be a hybrid of concepts from biogeography/metapopulation theory and behavioural ecology. [source] Can grazing response of herbaceous plants be predicted from simple vegetative traits?JOURNAL OF APPLIED ECOLOGY, Issue 3 2001Sandra Díaz Summary 1,Range management is based on the response of plant species and communities to grazing intensity. The identification of easily measured plant functional traits that consistently predict grazing response in a wide spectrum of rangelands would be a major advance. 2,Sets of species from temperate subhumid upland grasslands of Argentina and Israel, grazed by cattle, were analysed to find out whether: (i) plants with contrasting grazing responses differed in terms of easily measured vegetative and life-history traits; (ii) their grazing response could be predicted from those traits; (iii) these patterns differed between the two countries. Leaf mass, area, specific area (SLA) and toughness were measured on 83 Argentine and 19 Israeli species. Species were classified by grazing response (grazing-susceptible or grazing-resistant) and plant height (< or > 40 cm) as well as by life history (annual or perennial) and taxonomy (monocotyledon or dicotyledon). 3,Similar plant traits were associated with a specific response to grazing in both Argentina and Israel. Grazing-resistant species were shorter in height, and had smaller, more tender, leaves, with higher SLA than grazing-susceptible species. Grazing resistance was associated with both avoidance traits (small height and leaf size) and tolerance traits (high SLA). Leaf toughness did not contribute to grazing resistance and may be related to selection for canopy dominance. 4,Plant height was the best single predictor of grazing response, followed by leaf mass. The best prediction of species grazing response was achieved by combining plant height, life history and leaf mass. SLA was a comparatively poor predictor of grazing response. 5,The ranges of plant traits, and some correlation patterns between them, differed markedly between species sets from Argentina and Israel. However, the significant relationships between plant traits and grazing response were maintained. 6,The results of this exploratory study suggest that prediction of grazing responses on the basis of easily measured plant traits is feasible and consistent between similar grazing systems in different regions. The results challenge the precept that intense cattle grazing necessarily favours species with tough, unpalatable, leaves. [source] Forecasting US inflation by Bayesian model averagingJOURNAL OF FORECASTING, Issue 2 2009Jonathan H. Wright Abstract Recent empirical work has considered the prediction of inflation by combining the information in a large number of time series. One such method that has been found to give consistently good results consists of simple equal-weighted averaging of the forecasts from a large number of different models, each of which is a linear regression relating inflation to a single predictor and a lagged dependent variable. In this paper, I consider using Bayesian model averaging for pseudo out-of-sample prediction of US inflation, and find that it generally gives more accurate forecasts than simple equal-weighted averaging. This superior performance is consistent across subsamples and a number of inflation measures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Investigating the nature of expressiveness in stranger, acquaintance and intrafamilial homicidesJOURNAL OF INVESTIGATIVE PSYCHOLOGY AND OFFENDER PROFILING, Issue 3 2005Stephanie K. Last Abstract This study explores the role of the victim,offender relationship in the dynamics of homicide, by examining the crime scene behaviour of 25 intrafamilial, 30 acquaintance and 27 stranger homicide offenders (n = 82). Six crime scene variables were examined: ,Weapon from the scene', ,Excessive wounding', ,Facial trauma', ,Multiple wounds to a single area', ,Post-mortem activity' and ,Manual violence'. The first objective was to identify whether these variables could be combined to form a partially ordered scale of expressiveness. The second was to examine whether the nature of this expressive crime scene varied according to the victim and offender relationship. It was hypothesised that the intrafamilial homicides would be characterised by a more expressive crime scene. This was examined by Partial Order Scalogram Analysis which supported the hypothesised link between the level of expressed emotion evident in the crime scene and the nature of the victim,offender relationship. Further analysis on the individual variables revealed that the best single predictor of the relationship between victim and offender was the presence of multiple wounding. These findings are discussed both as contributing to a theoretical understanding of the emotional salience of crime scene actions when killing a family member, and in practical terms in relation to the significance of these variables for both police investigations and clinical interventions with homicide perpetrators. Copyright © 2005 John Wiley & Sons, Ltd. [source] The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and painJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2002D. E. Hurwitz This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = ,0.33 to ,0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = ,0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10,18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Desmopressin treatment in nocturia; an analysis of risk factors for hyponatremiaNEUROUROLOGY AND URODYNAMICS, Issue 2 2006A. Rembratt Abstract Aims To explore the incidence, severity, time course, and risk factors of clinically significant hyponatremia in desmopressin treatment for nocturia. Methods Data from three multi-center phase III trials were pooled. Hyponatremia was categorised as borderline (134,130 mmol/L) or significant (<130 mmol/L). Risk factors were explored with logistic regression and subgroup analysis performed to explore threshold values for contra-indication. Results In total 632 patients (344 men, 288 women) were analyzed. During dose-titration, serum sodium concentration below normal range was recorded in 95 patients (15%) and 31 patients (4.9%) experienced significant hyponatremia. The risk increased with age, lower serum sodium concentration at baseline, higher basal 24-hr urine volume per bodyweight and weight gain at time of minimum serum sodium concentration. Age was the best single predictor. Elderly patients (,65 years of age) with a baseline serum sodium concentration below normal range were at high risk (75%). Limiting treatment in elderly with normal basal serum sodium concentration to those below 79 years and with a 24-hr urine output below 28 ml/kg would reduce the risk from 8.1% to 3.0% at the cost of 34% fulfilling the contra-indication. Conclusions The majority of nocturia patients tolerate desmopressin treatment without clinically significant hyponatremia. However, the risk increases with increasing age and decreasing baseline serum sodium concentration. Treatment of nocturia in elderly patients with desmopressin should only be undertaken together with careful monitoring of the serum sodium concentration. Patients with a baseline serum sodium concentration below normal range should not be treated. © 2005 Wiley-Liss, Inc. [source] ESTIMATION, PREDICTION AND INFERENCE FOR THE LASSO RANDOM EFFECTS MODELAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2009Scott D. Foster Summary The least absolute shrinkage and selection operator (LASSO) can be formulated as a random effects model with an associated variance parameter that can be estimated with other components of variance. In this paper, estimation of the variance parameters is performed by means of an approximation to the marginal likelihood of the observed outcomes. The approximation is based on an alternative but equivalent formulation of the LASSO random effects model. Predictions can be made using point summaries of the predictive distribution of the random effects given the data with the parameters set to their estimated values. The standard LASSO method uses the mode of this distribution as the predictor. It is not the only choice, and a number of other possibilities are defined and empirically assessed in this article. The predictive mode is competitive with the predictive mean (best predictor), but no single predictor performs best across in all situations. Inference for the LASSO random effects is performed using predictive probability statements, which are more appropriate under the random effects formulation than tests of hypothesis. [source] Restraint safety in a residential setting for persons with intellectual disabilitiesBEHAVIORAL INTERVENTIONS, Issue 2 2009David M. Tilli The primary purpose of this study was to estimate the risks associated with the use of emergency personal restraints at a residential facility for persons with intellectual and developmental disabilities. A secondary purpose was to determine if correlates of restraint-related injury could be determined. One in three restraints resulted in an injury, but all of the injuries were minor. In terms of prediction, frequency of aggressive behavior use was the best single predictor of restraint-related injury. Copyright © 2009 John Wiley & Sons, Ltd. [source] Socioeconomic indicators and prosthetic replacement of missing teeth in a working-age population,Results of the Study of Health in Pomerania (SHIP)COMMUNITY DENTISTRY AND ORAL EPIDEMIOLOGY, Issue 2 2009Torsten Mundt Abstract,,, Objectives:, To analyse the possible effects of the socioeconomic status (SES) on the prosthetic replacement of missing teeth in working-age people and to explore the role of potential confounders. Methods:, Cross-sectional data were collected from 2310 German adults aged 30,59 years. The relationship between each of the three SES indicators (education, income, and occupational status) and dental prostheses were examined by multinomial logistic regression analyses. For that, partially dentate participants with suboptimal and no replacement of missing teeth were compared with partially dentate participants having optimal replacement. Potential confounders (age, sex, dental status, social network and social support) were entered if their inclusion in the model led to ,10% change in the coefficient of interest. Results:, Social network and social support did not meet the criterion for confounding. In the maxilla, having no replacement was positively associated with lower categories for each of the three SES indicators [Odds ratios (OR) between 1.6 and 2.1; 95% confidence intervals (CI) between 1.1 and 3.4]. Low occupational status was the single predictor for suboptimal dental prostheses (OR = 3.2; 95% CI: 1.6,6.2). In the mandible, occupational status showed no association with the prosthetic status, whereas low educational level and low household income were determinants for having no replacement (OR = 1.9 and 1.9, 95% CI: 1.0,3.5 and 1.1,3.0, respectively). Low household income was the single determinant for suboptimal replacement of missing teeth (OR = 2.4, 95% CI = 1.1,5.2). Conclusion:, The findings may indicate the relevance of the financing of prosthodontic treatment. The strong association between various forms of upper dentures and occupational prestige can be seen as key contributing concept to how individuals, characteristics affect the outcome in prosthodontic care. [source] | ||||||||||||||||