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Conventional Analysis (conventional + analysis)
Selected AbstractsEnvironmental power analysis , a new perspectiveENVIRONMETRICS, Issue 5 2001David R. Fox Abstract Power analysis and sample-size determination are related tools that have recently gained popularity in the environmental sciences. Their indiscriminate application, however, can lead to wildly misleading results. This is particularly true in environmental monitoring and assessment, where the quality and nature of data is such that the implicit assumptions underpinning power and sample-size calculations are difficult to justify. When the assumptions are reasonably met these statistical techniques provide researchers with an important capability for the allocation of scarce and expensive resources to detect putative impact or change. Conventional analyses are predicated on a general linear model and normal distribution theory with statistical tests of environmental impact couched in terms of changes in a population mean. While these are ,optimal' statistical tests (uniformly most powerful), they nevertheless pose considerable practical difficulties for the researcher. Compounding this difficulty is the subsequent analysis of the data and the impost of a decision framework that commences with an assumption of ,no effect'. This assumption is only discarded when the sample data indicate demonstrable evidence to the contrary. The alternative (,green') view is that any anthropogenic activity has an impact on the environment and therefore a more realistic initial position is to assume that the environment is already impacted. In this article we examine these issues and provide a re-formulation of conventional mean-based hypotheses in terms of population percentiles. Prior information or belief concerning the probability of exceeding a criterion is incorporated into the power analysis using a Bayesian approach. Finally, a new statistic is introduced which attempts to balance the overall power regardless of the decision framework adopted. Copyright © 2001 John Wiley & Sons, Ltd. [source] Estimating causal effects from observational data with a model for multiple biasINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 2 2007Michael Höfler Abstract Conventional analyses of observational data may be biased due to confounding, sampling and measurement, and may yield interval estimates that are much too narrow because they do not take into account uncertainty about unknown bias parameters, such as misclassification probabilities. We used a simple, multiple bias adjustment method to estimate the causal effect of social anxiety disorder (SAD) on subsequent depression. A Monte Carlo sensitivity analysis was applied to data from the Early Developmental Stages of Psychiatry (EDSP) study, and bias due to confounding, sampling and measurement was modelled. With conventional logistic regression analysis, the risk for depression was elevated in the presence of SAD only in the older cohort (age 17,24 years at baseline assessment); odds ratio (OR) = 3.06, 95% confidence interval (CI) 1.64,5.70, adjusted for sex and age. The bias-adjusted estimate was 2.01 with interval limits of 0.61 and 9.71. Thus, given the data and the bias model used, there was considerably more uncertainty about the real effect, but the probability that SAD increases the risk for subsequent depression (OR > 1) was 88.6% anyway. Multiple bias modelling, if properly used, reveals the necessity for a better understanding of bias, suggesting a need to conduct larger and more adequate validation studies on instruments that are used to diagnose mental disorders. Copyright © 2007 John Wiley & Sons, Ltd. [source] Impact of advanced exercise ECG analysis on cost of coronary artery disease managementJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 4 2010Riccardo Bigi PhD Abstract Background, Conventional analysis of exercise electrocardiogram (EX-ECG) has limited accuracy. This study aims to evaluate the potential impact of improving EX-ECG accuracy on costs of diagnosis and number of misdiagnoses of coronary artery disease (CAD). Methods, A decision-tree model was simulated including sequential application of diagnostic procedures for suspected CAD. The model was structured in two main branches (presence or absence of CAD). A probabilistic sensitivity analysis was then performed for several combinations of improvement in test sensitivity and specificity. Results, A clear trend in cost reduction was observed at improving EX-ECG specificity (about 8,8.5 million dollars, corresponding to a 5.6,7.6% reduction according to the prevalence level). Wrong diagnoses counted for 9,13% of test. Improvements in test parameters lead to reductions in wrong diagnoses, especially when increasing specificity (8.8,12.5%). Conclusions, A proper improvement in EX-ECG sensitivity and specificity would have a relevant impact on the costs of CAD management, while reducing the number of misdiagnoses. [source] The elusive intermediate on the folding pathway of the prion proteinFEBS JOURNAL, Issue 6 2008David C. Jenkins A key molecular event in prion diseases is the conversion of the cellular conformation of the prion protein (PrPC) to an altered disease-associated form, generally denoted as scrapie isoform (PrPSc). The molecular details of this conformational transition are not fully understood, but it has been suggested that an intermediate on the folding pathway of PrPC may be recruited to form PrPSc. In order to investigate the folding pathway of PrP we designed and expressed two mutants, each possessing a single strategically located tryptophan residue. The secondary structure and folding properties of the mutants were examined. Using conventional analyses of folding transition data determined by fluorescence and CD, and novel phase-diagram analyses, we present compelling evidence for the presence of an intermediate species on the folding pathway of PrP. The potential role of this intermediate in prion conversion is discussed. [source] Differential transient MEG and fMRI responses to visual stimulation onset rateINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2008August S. Tuan Abstract While recent analysis of functional magnetic resonance imaging (fMRI) data utilize a generalized nonlinear convolution model (e.g., dynamic causal modeling), most conventional analyses of local responses utilize a linear convolution model (e.g., the general linear model). These models assume a linear relationship between the blood oxygenated level dependent (BOLD) signal and the underlying neuronal response. While previous studies have shown that this "neurovascular coupling" process is approximately linear, short stimulus durations are known to produce a larger fMRI response than expected from a linear system. This divergence from linearity between the stimulus time-course and BOLD signal could be caused by neuronal onset and offset transients, rather than a nonlinearity in the hemodynamics related to BOLD contrast. We tested this hypothesis by measuring MEG and fMRI responses to stimuli with ramped contrast onsets and offsets in place of abrupt transitions. MEG results show that the ramp successfully reduced the transient onset of neural activity. However, the nonlinearity in the fMRI response, while also reduced, remained. Predictions of fMRI responses from MEG signals show a weaker nonlinearity than observed in the actual fMRI data. These results suggest that the fMRI BOLD nonlinearity seen with short duration stimuli is not solely due to transient neuronal activity. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 18, 17,28, 2008 [source] Diet composition, rumen papillation and maintenance of carcass mass in female Norwegian reindeer (Rangifer tarandus tarandus) in winterJOURNAL OF ZOOLOGY, Issue 1 2000S. D. Mathiesen Abstract The uptake of volatile fatty acids (VFAs) from bacterial fermentation of forage in the rumen is enhanced by the presence of papillae which greatly increase the surface area of the mucosa of the rumen. The degree of papillation, expressed as the surface enlargement factor (SEF), seems to be closely related to the level of microbial activity and the rate of production of VFAs in the rumen. In several species of wild ruminants the SEF decreases markedly in winter, apparently in response to a decrease in the quality and availability of forage and also, presumably, in the level of ruminal microbial activity. Contrary to expectation, however, no reduction in the rate of production of VFAs in winter has been detected in semi-domesticated reindeer at natural pasture in northern Norway. We investigated the body mass, the composition and quality of the diet and the morphology of rumen papillae in adult female reindeer free-living at natural pasture. Animals were slaughtered in matched aged groups of nine on four occasions: in autumn (September) and winter (November, February and March). The composition and quality of the diet was determined by morphological and chemical analysis of plant fragments recovered from the rumen. The carcass mass of the animals did not differ significantly between collections. The animals ate vascular plants and lichens from 37 different genera. The composition of the diet varied little between months except for the inclusion of a substantial proportion (25.8% of fragments) of lichens in March. The mean density of rumen papillae increased from 55.6 papillae/cm2 in September to 75.7 papillae/cm2 in March (P < 0.001). All other parameters, including the length and perimeter of the papillae and the SEF of the rumen, were lower in March compared with September. However, the mean SEF increased from 8.8 in February to 10.6 in March (P < 0.05), indicating increased ruminal fermentation in late winter. We propose that the increase in the SEF in March might be associated with the increase in the proportion of lichens in the diet. Lichens are highly digestible in reindeer but do not score highly in conventional analyses of diet quality owing to the unusual chemical structure of the structural carbohydrates of which they are composed. [source] The diffusion of regulatory impact analysis , Best practice or lesson-drawing?EUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 5 2004CLAUDIO M. RADAELLI Its main theoretical thrust is to explore the limitations of the conventional analysis of RIA in terms of de-contextualised best practice and provide an alternative framework based on the lesson-drawing literature. After having discussed how demand and supply of best practice emerge in the OECD and the European Union, some analytic (as opposed to normative) lessons are presented. The main lessons revolve around the politics of problem definition, the nesting of RIA into wider reform programmes, the political malleability of RIA, the trade-off between precision and administrative assimilation, the roles of networks and watchdogs, and institutional learning. The conclusions discuss the implications of the findings for future research. [source] Numerical study of grid distribution effect on accuracy of DQ analysis of beams and plates by error estimation of derivative approximationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2001C. Shu Abstract The accuracy of global methods such as the differential quadrature (DQ) approach is usually sensitive to the grid point distribution. This paper is to numerically study the effect of grid point distribution on the accuracy of DQ solution for beams and plates. It was found that the stretching of grid towards the boundary can improve the accuracy of DQ solution, especially for coarse meshes. The optimal grid point distribution (corresponding to optimal stretching parameter) depends on the order of derivatives in the boundary condition and the number of grid points used. The optimal grid distribution may not be from the roots of orthogonal polynomials. This differs somewhat from the conventional analysis. This paper also proposes a simple and effective formulation for stretching the grid towards the boundary. The error distribution of derivative approximation is also studied, and used to analyze the effect of grid point distribution on accuracy of numerical solutions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Relationship between host diversity and parasite diversity: flea assemblages on small mammalsJOURNAL OF BIOGEOGRAPHY, Issue 11 2004Boris R. Krasnov Abstract Aim, We examined the relationship between host species richness and parasite species richness using simultaneously collected data on small mammals (Insectivora, Rodentia and Lagomorpha) and their flea parasites. Location, The study used previously published data on small mammals and their fleas from 37 different regions. All the world's main geographical regions other than Australasia and Wallacea were represented in the study, i.e. neotropical, nearctic, palaearctic, oriental and afrotropical realms. Methods, We controlled the data for the area sampled and sampling effort and then tested this relationship using both cross-region conventional analysis and the independent contrasts method (to control for the effects of biogeographic historical relationships among different regions). Brooks parsimony analysis was used to construct a region cladogram based on the presence/absence of a host species and host phylogeny. Results, Both cross-region and independent contrasts analyses showed a positive correlation between host species richness and flea species richness. Conventional cross-region regression under- or overestimated fleas species richness in the majority of regions. Main conclusions, When the regression derived by the independent contrasts method was mapped onto the original tip data space, points that deviated significantly from the regression originated from Kenya, Mississippi and southern California (lower than expected flea richness) and Chile, Idaho, south-western California and Kyrgyzstan (higher than expected flea richness). These deviations can be explained by the environmental mediation of host,flea relationships and by a degree of environmental variety in sampled areas. [source] The Environmental Civil Society and the Transformation of State-Society Relations in China: Building a Tri-level Analytical FrameworkPACIFIC FOCUS, Issue 2 2007Teh-chang Lin State-society relations is a conventional tool used in analyzing the relational behavioral pattern of between the state and the society. In China, market reforms and open policy since 1978 have engendered the growth of environmental civil society organizations and thereby enhanced the changes in the nature of state-society relations. However, the analysis of Chinese state-society relations has in the past largely been two-dimensional, focusing on domestic relations. However, changing patterns of state-society relations in China has called for a more elaborate tri-level analytical framework of the state, its main civil society representative, domestic non-governmental organizations, and international non-governmental organizations. Through the study of environmental protests such as anti-dam construction demonstrations, we have found that domestically, Chinese environmental nongovernmental organizations not only act as a challenger to the state, but at times collaborate with the state. From an external perspective, international non-governmental organizations not only directly challenge the Chinese state, but also network with local Chinese NGOs in their protests. This article thus adds a new level to the conventional analysis of state-society relations in China. [source] An application of hierarchical regression in the investigation of multiple paternal occupational exposures and neuroblastoma in offspring,AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 5 2001Anneclaire J. De Roos MPH Abstract Background We used hierarchical regression to study the effects of 46 paternal occupational exposures on the incidence of neuroblastoma in offspring. Methods The study population included 405 cases and 302 controls. The effect of each exposure was estimated using both conventional maximum likelihood and hierarchical regression. Results Using hierarchical regression, overall precision was greatly enhanced compared to the conventional analysis. In addition, adjustment of effect estimates based on prespecified prior distributions of the true effect parameters allowed a more consistent interpretation across the entire panel of exposures. Estimates for several metals and solvents were shrunk close to the null value, whereas estimates for several thinner solvents, diesel fuel, solders, wood dust, and grain dust remained moderately elevated. Conclusions Hierarchical regression may mitigate some of the problems of the conventional approach by controlling for correlated exposures, enhancing the precision of estimates, and providing some adjustment of estimates based on prior knowledge. Am. J. Ind. Med. 39:477,486, 2001. © 2001 Wiley-Liss, Inc. [source] CASA-based sperm kinematics of environmental risk factor-exposed human semen samples designated as normozoospermic in conventional analysisANDROLOGIA, Issue 4 2010D. Mukhopadhyay Summary This study was conducted after an initial epidemiological survey of patients in and around Calcutta, India, concerning their lifestyle history, degree of risk exposure and semen analysis based on conventional WHO criteria. It was found that a large group of exposed patients were showing normozoospermic semen parameters in conventional semen analysis. Hence, a selected group of subjects, designated as normozoospermic in routine analysis, but under risk factor exposure, were selected for a repeat computer aided semen analysis (CASA) and were compared with a control group. The parameters considered among CASA results were: curvilinear velocity (VCL), straight-line velocity, average path velocity (VAP), straightness index (STR), lateral head displacement (ALH) and beat cross frequency. The results depict a significant decline in the mean values of VCL (P = 0.029) and STR (P = 0.007) in the tobacco-exposed group when compared with the unexposed group. On the other hand, there was a significant decline in the mean values of VCL (P = 0.014) and ALH (P = 0.040) in the heavy metal-exposed group when compared with the unexposed group. The other parameters did not show significant change in either group. Semen samples that had been designated normozoospermic in conventional analysis were seen to be influenced by risk factors at the level of sperm motion kinetics. [source] | |||||||||||||