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Continuous Scale (continuous + scale)

Distribution by Scientific Domains

Medical Sciences	33%
Psychology	16%
Life Sciences	16%

Selected Abstracts

Performance of Greater Sage-Grouse Models for Conservation Assessment in the Interior Columbia Basin, U.S.A.

CONSERVATION BIOLOGY, Issue 5 2002
Michael J. Wisdom
Consequently, we evaluated the performance of two models designed to assess landscape conditions for Greater Sage-Grouse across 13.6 million ha of sagebrush steppe in the interior Columbia Basin and adjacent portions of the Great Basin of the western United States (referred to as the basin). The first model, the environmental index model, predicted conditions at the scale of the subwatershed (mean size of approximately 7800 ha) based on inputs of habitat density, habitat quality, and effects of human disturbance. Predictions ranged on a continuous scale from 0 for lowest environmental index to 2 for optimal environmental index. The second model, the population outcome model, predicted the composite, range-wide conditions for sage grouse based on the contribution of environmental index values from all subwatersheds and measures of range extent and connectivity. Population outcomes were expressed as five classes (A through E) that represented a gradient from continuous, well-distributed populations (outcome A) to sparse, highly isolated populations with a high likelihood of extirpation (outcome E). To evaluate performance, we predicted environmental index values and population outcome classes in areas currently occupied by sage grouse versus areas where extirpation has occurred. Our a priori expectations were that models should predict substantially worse environmental conditions ( lower environmental index) and a substantially higher probability of extirpation ( lower population outcome class) in extirpated areas. Results for both models met these expectations. For example, a population outcome of class E was predicted for extirpated areas, as opposed to class C for occupied areas. These results suggest that our models provided reliable landscape predictions for the conditions tested. This finding is important for conservation planning in the basin, where the models were used to evaluate management of federal lands for sage grouse. Resumen: Modelos válidos de hábitat y de poblaciones del urogallo (Centrocercus urophasianus) son una necesidad crítica para su manejo debido a la creciente preocupación por la viabilidad de la población. Por lo tanto, evaluamos el funcionamiento de dos modelos diseñados para evaluar las condiciones del paisaje para el urogallo en 13.6 millones de ha de la estepa de artemisa en la Cuenca Columbia Interior y las porciones adyacentes de la Gran Cuenca de los Estados Unidos occidentales (referidos como cuenca). El primer modelo (modelo de índice ambiental) predijo condiciones a escala de la subcuenca (tamaño promedio , 7800 ha) basado en información de la densidad del hábitat, calidad del hábitat y efectos de la perturbación humana. Las predicciones variaron en una escala continua a partir de 0 (el índice ambiental más bajo) a 2 (índice ambiental óptimo). El segundo modelo (modelo del resultado de la población) predijo las condiciones compuestas, de amplio rango, para el urogallo con base en la contribución de los valores de índice ambiental de todas las subcuencas y las medidas de extensión y de conectividad de la pradera. Los resultados de la población fueron expresados en cinco clases (A - E) que representan un gradiente de poblaciones continuas, bien-distribuidas (resultado A) a poblaciones escasas, altamente aisladas con una alta probabilidad de extirpación (resultado E). Para evaluar el funcionamiento, predijimos valores de índice ambiental y resultados de la población en las áreas actualmente ocupadas por urogallos versus áreas donde ha ocurrido la extirpación. Nuestras expectativas a priori eran que los modelos deben predecir condiciones ambientales substancialmente peores (índice ambiental más bajo) y una probabilidad de extirpación sustancialmente mayor (menor resultado de la población) en áreas extirpadas. Los resultados para ambos modelos cumplieron estas expectativas. Por ejemplo, se predijo un resultado de la población de la clase E para áreas extirpadas, en comparación con la clase C para áreas ocupadas. Estos resultados sugieren que nuestros modelos proporcionaron predicciones de paisaje confiables para las condiciones probadas. Este hallazgo es importante para planeación de la conservación de la cuenca, donde los modelos fueron utilizados para evaluar el manejo de terrenos federales para urogallos. [source]

Overweight and obesity and incidence of leukemia: A meta-analysis of cohort studies

INTERNATIONAL JOURNAL OF CANCER, Issue 6 2008
Susanna C. Larsson
Abstract We conducted a meta-analysis to summarize the available evidence from cohort studies on the association between excess body weight and incidence of leukemia. Studies were identified by searching the MEDLINE and EMBASE databases (1966,July 2007) and by examining the references of retrieved articles. A random-effects model was used to combine the results from individual studies. We identified 9 cohort studies with data on body mass index (BMI) or obesity in relation to incidence of leukemia. Compared with nonoverweight individuals (BMI < 25 kg/m2), the summary relative risks (RRs) of leukemia were 1.14 [95% confidence interval (CI), 1.03,1.25] for overweight individuals (BMI 25,30 kg/m2) and 1.39 (95% CI, 1.25,1.54) for obese (BMI , 30 kg/m2) individuals. On a continuous scale, a 5 kg/m2 increase in BMI was associated with a 13% increased risk of leukemia (RR, 1.13; 95% CI, 1.07,1.19). In a meta-analysis of 4 studies reporting results on subtypes of leukemia, the summary RRs associated with obesity were 1.25 (95% CI, 1.11,1.41) for chronic lymphocytic leukemia, 1.65 (95% CI, 1.16,2.35) for acute lymphocytic leukemia, 1.52 (95% CI, 1.19,1.95) for acute myeloid leukemia and 1.26 (95% CI, 1.09,1.46) for chronic myeloid leukemia. This meta-analysis indicates that excess body weight is associated with an increased risk of developing leukemia. © 2007 Wiley-Liss, Inc. [source]

Photographic scoring of gingival overgrowth

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2001
J. S. Ellis
Abstract Background: A wide range of methods have been employed to determine the severity of gingival overgrowth resulting in uncertainty regarding the prevalence of the side-effect. There is no simple, non-invasive, objective, blind method for assessing gingival overgrowth. Aim: This article aims to describe a method which is suitable for use in large-scale population studies. Materials and Methods: Photographs were taken of the anterior, buccal gingivae and teeth of 925 patients medicated with calcium channel blockers. In addition, each patient was ascribed a clinical gingival overgrowth score. 100 patients had repeat photographs, and a further 10 patients had alginate impressions taken. The models were scored for severity of gingival overgrowth using a described technique. The slides were scored using a modification of this technique. Results: When photographic and study model scores were compared, photographic scores were consistently higher, and as a result, a photographic score of 38.6% was considered to represent a significant overgrowth. There was good agreement between clinically determined scores and photographic scores (,=0.71). Conclusions: The results indicate that this method is suitable for large-scale population studies where it also has the advantage of providing a continuous scale of gingival changes for subsequent statistical analysis. [source]

Interfragmentary surface area as an index of comminution severity in cortical bone impact

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2005
Christina L. Beardsley
Abstract A monotonic relationship is expected between energy absorption and fracture surface area generation for brittle solids, based on fracture mechanics principles. It was hypothesized that this relationship is demonstrable in bone, to the point that on a continuous scale, comminuted fractures created with specific levels of energy delivery could be discriminated from one another. Using bovine cortical bone segments in conjunction with digital image analysis of CT fracture data, the surface area freed by controlled impact fracture events was measured. The results demonstrated a statistically significant (p < 0.0001) difference in measured de novo surface area between three specimen groups, over a range of input energies from 0.423 to 0.702 J/g. Local material properties were also incorporated into these measurements via CT Hounsfield intensities. This study confirms that comminution severity of bone fractures can indeed be measured on a continuous scale, based on energy absorption. This lays a foundation for similar assessments in human injuries. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Review of multinomial and multiattribute quality control charts

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 7 2009
Elisabeth Topalidou
Abstract Attribute control charts are very useful nowadays for monitoring processes where the quality characteristics cannot be measured in a continuous scale, which may be manufacturing processes from industrial settings, health-care processes or processes from service industries and environments of non-manufacturing quality-improvement efforts. Many of the above cases, however, involve the monitoring of multiple attributes simultaneously, thus leading to the case of multinomial and multiattribute quality control methods, which are better than the simultaneous use of multiple uni-attribute methods. In this study, an attempt to review the research previously conducted on multiattribute quality control is made in order to help the interested researchers and practitioners get informed about the references on the relevant research in this field, regarding the design, performance and applications of multiattribute control charts. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Mother,child joint activity and behaviour problems of pre-school children

THE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2003
Kumari Chandani Galboda-Liyanage
Background: Behaviour problems are common among pre-school children, and a substantial proportion persist, causing significant burden to the family, schools and health services. Relatively little research has addressed the effects of positive parenting on behaviour disorder in pre-school children, particularly in larger population-based studies. Method: A cross-sectional postal survey of a representative, population-based sample of 800 mothers of 3½-year-old children living in an outer London Borough was carried out to assess the association between mother,child joint activity and behaviour problems of pre-school children. The response rate was 70%. Results: Lower levels of mother,child joint activity remained independently associated with behaviour problems of pre-school children both on a binary and a continuous scale after adjusting for a wide range of household, maternal and child circumstances. The association between low levels of mother,child joint activities and behaviour problems of the children was stronger in the presence of social problems in the family. Conclusion: Possible causal pathways and directions for future research and intervention are discussed. [source]

Semiparametric Models of Time-Dependent Predictive Values of Prognostic Biomarkers

BIOMETRICS, Issue 1 2010
Yingye Zheng
Summary Rigorous statistical evaluation of the predictive values of novel biomarkers is critical prior to applying novel biomarkers into routine standard care. It is important to identify factors that influence the performance of a biomarker in order to determine the optimal conditions for test performance. We propose a covariate-specific time-dependent positive predictive values curve to quantify the predictive accuracy of a prognostic marker measured on a continuous scale and with censored failure time outcome. The covariate effect is accommodated with a semiparametric regression model framework. In particular, we adopt a smoothed survival time regression technique (Dabrowska, 1997,,The Annals of Statistics,25, 1510,1540) to account for the situation where risk for the disease occurrence and progression is likely to change over time. In addition, we provide asymptotic distribution theory and resampling-based procedures for making statistical inference on the covariate-specific positive predictive values. We illustrate our approach with numerical studies and a dataset from a prostate cancer study. [source]

A New Nonparametric Approach for Baseline Covariate Adjustment for Two-Group Comparative Studies

BIOMETRICS, Issue 4 2008
Alexander Schacht
Summary We consider two-armed clinical trials in which the response and/or the covariates are observed on either a binary, ordinal, or continuous scale. A new general nonparametric (NP) approach for covariate adjustment is presented using the notion of a relative effect to describe treatment effects. The relative effect is defined by the probability of observing a higher response in the experimental than in the control arm. The notion is invariant under monotone transformations of the data and is therefore especially suitable for ordinal data. For a normal or binary distributed response the relative effect is the transformed effect size or the difference of response probability, respectively. An unbiased and consistent NP estimator for the relative effect is presented. Further, we suggest a NP procedure for correcting the relative effect for covariate imbalance and random covariate imbalance, yielding a consistent estimator for the adjusted relative effect. Asymptotic theory has been developed to derive test statistics and confidence intervals. The test statistic is based on the joint behavior of the estimated relative effect for the response and the covariates. It is shown that the test statistic can be used to evaluate the treatment effect in the presence of (random) covariate imbalance. Approximations for small sample sizes are considered as well. The sampling behavior of the estimator of the adjusted relative effect is examined. We also compare the probability of a type I error and the power of our approach to standard covariate adjustment methods by means of a simulation study. Finally, our approach is illustrated on three studies involving ordinal responses and covariates. [source]

Estimating the Generalized Concordance Correlation Coefficient through Variance Components

BIOMETRICS, Issue 4 2003
Josep L. Carrasco
Summary. The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) are two of the most popular measures of agreement for variables measured on a continuous scale. Here, we demonstrate that ICC and CCC are the same measure of agreement estimated in two ways: by the variance components procedure and by the moment method. We propose estimating the CCC using variance components of a mixed effects model, instead of the common method of moments. With the variance components approach, the CCC can easily be extended to more than two observers, and adjusted using confounding covariates, by incorporating them in the mixed model. A simulation study is carried out to compare the variance components approach with the moment method. The importance of adjusting by confounding covariates is illustrated with a case example. [source]

Does Amount of Time Spent in Child Care Predict Socioemotional Adjustment During the Transition to Kindergarten?

CHILD DEVELOPMENT, Issue 4 2003
Early Child Care Research Network, Human Development, National Institute of Child Health
To examine relations between time in nonmaternal care through the first 4.5 years of life and children's socioemotional adjustment, data on social competence and problem behavior were examined when children participating in the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care were 4.5 years of age and when in kindergarten. The more time children spent in any of a variety of nonmaternal care arrangements across the first 4.5 years of life, the more externalizing problems and conflict with adults they manifested at 54 months of age and in kindergarten, as reported by mothers, caregivers, and teachers. These effects remained, for the most part, even when quality, type, and instability of child care were controlled, and when maternal sensitivity and other family background factors were taken into account. The magnitude of quantity of care effects were modest and smaller than those of maternal sensitivity and indicators of family socioeconomic status, though typically greater than those of other features of child care, maternal depression, and infant temperament. There was no apparent threshold for quantity effects. More time in care not only predicted problem behavior measured on a continuous scale in a dose-response pattern but also predicted at-risk (though not clinical) levels of problem behavior, as well as assertiveness, disobedience, and aggression. [source]

Understanding diagnostic tests 3: receiver operating characteristic curves

ACTA PAEDIATRICA, Issue 5 2007
Anthony K Akobeng
Abstract The results of many clinical tests are quantitative and are provided on a continuous scale. To help decide the presence or absence of disease, a cut-off point for ,normal' or ,abnormal' is chosen. The sensitivity and specificity of a test vary according to the level that is chosen as the cut-off point. The receiver operating characteristic (ROC) curve, a graphical technique for describing and comparing the accuracy of diagnostic tests, is obtained by plotting the sensitivity of a test on the y axis against 1-specificity on the x axis. Two methods commonly used to establish the optimal cut-off point include the point on the ROC curve closest to (0, 1) and the Youden index. The area under the ROC curve provides a measure of the overall performance of a diagnostic test. In this paper, the author explains how the ROC curve can be used to select optimal cut-off points for a test result, to assess the diagnostic accuracy of a test, and to compare the usefulness of tests. Conclusion: The ROC curve is obtained by calculating the sensitivity and specificity of a test at every possible cut-off point, and plotting sensitivity against 1-specificity. The curve may be used to select optimal cut-off values for a test result, to assess the diagnostic accuracy of a test, and to compare the usefulness of different tests. [source]

Is the placebo powerless?

JOURNAL OF INTERNAL MEDICINE, Issue 2 2004
Update of a systematic review with 52 new randomized trials comparing placebo with no treatment
Abstract. Background., It is widely believed that placebo interventions induce powerful effects. We could not confirm this in a systematic review of 114 randomized trials that compared placebo-treated with untreated patients. Aim., To study whether a new sample of trials would reproduce our earlier findings, and to update the review. Methods., Systematic review of trials that were published since our last search (or not previously identified), and of all available trials. Results., Data was available in 42 out of 52 new trials (3212 patients). The results were similar to our previous findings. The updated review summarizes data from 156 trials (11 737 patients). We found no statistically significant pooled effect in 38 trials with binary outcomes, relative risk 0.95 (95% confidence interval 0.89,1.01). The effect on continuous outcomes decreased with increasing sample size, and there was considerable variation in effect also between large trials; the effect estimates should therefore be interpreted cautiously. If this bias is disregarded, the pooled standardized mean difference in 118 trials with continuous outcomes was ,0.24 (,0.31 to ,0.17). For trials with patient-reported outcomes the effect was ,0.30 (,0.38 to ,0.21), but only ,0.10 (,0.20 to 0.01) for trials with observer-reported outcomes. Of 10 clinical conditions investigated in three trials or more, placebo had a statistically significant pooled effect only on pain or phobia on continuous scales. Conclusion., We found no evidence of a generally large effect of placebo interventions. A possible small effect on patient-reported continuous outcomes, especially pain, could not be clearly distinguished from bias. [source]