Search results for "Statistical"
showing 10 items of 4960 documents
Adaptive trial design: a general methodology for censored time to event data.
2008
Adaptive designs allow a clinical trial design to be changed according to interim findings without inflating type I error. The Inverse Normal method can be considered as an adaptive generalization of classical group sequential designs. The use of the Inverse Normal method for censored survival data was demonstrated only for the logrank statistic. However, the logrank statistic is inefficient in the presence of nuisance covariates affecting survival. We demonstrate, how the Inverse Normal method can be applied to Cox regression analysis. The required independence between test statistics of the different stages of the trial can be obtained by two different approaches. One is using the indepen…
VIII: Statistik in klinischen Publikationen: Checklisten für Autoren
2003
The "Material and Methods" section of clinical research papers should reference major aspects concerning statistical planning and evaluation of the study design and the resulting clinical data. Particular focus is laid on the listing of methods for description and significance evaluation of the trial data, as well as on design-associated study determinants (randomisation and masking strategy, response rate evaluation, primary endpoints, power and sample size determination, multiple testing, software and methods for statistical analysis). Suggestions for the minimum content to be mentioned in a trial publication are listed in author check lists and are illustrated by means of the study synop…
V: p-Werte: Was sie besagen und was nicht …
2002
Both an extensive data description and an explicit assessment of a study result's statistical significance should be presented in the result section of a clinical trial report. Whereas the description illustrates the order and clinical relevance of the study findings, the statistical significance describes its generalizability to patients not included in the clinical trial: Despite the random recruitment of patients into a trial, the study results may fail to represent clinical reality (for example the trial might show falsely positive efficacy findings, whereas in "clinical reality" efficacy appears rather limited). A p value measures the statistical significance of a study result -- the s…
Temperamento y crianza en la construcción de la personalidad. conducta agresiva, inestabilidad y prosociabilidad [Effect of temperament and upbringin…
2004
Resumen La investigacion realizada persigue un doble objetivo. El primero se dirige a estudiar la relacion que se establece entre la estructura de la personalidad del adolescente y la manifestacion de la agresion, de la inestabilidad emocional y de la conducta prosocial. El segundo objetivo pretende analizar del peso que muestran los habitos de crianza en la emision de las conductas agresivas, inestables y prosociales. La muestra esta constituida por 531 adolescentes, chicos y chicas de edades comprendidas entre los 12 y los 16 anos, escolarizados en Centros Publicos y Concertados, que cursan la Etapa Educativa de la Educacion Secundaria Obligatoria. En atencion al procedimiento aleatorio, …
GenClust: A genetic algorithm for clustering gene expression data
2005
Abstract Background Clustering is a key step in the analysis of gene expression data, and in fact, many classical clustering algorithms are used, or more innovative ones have been designed and validated for the task. Despite the widespread use of artificial intelligence techniques in bioinformatics and, more generally, data analysis, there are very few clustering algorithms based on the genetic paradigm, yet that paradigm has great potential in finding good heuristic solutions to a difficult optimization problem such as clustering. Results GenClust is a new genetic algorithm for clustering gene expression data. It has two key features: (a) a novel coding of the search space that is simple, …
A fast and efficient modified sectional method for simulating multicomponent collisional kinetics
1999
A fast and efficient method for simulating the evolution of internally mixed multicomponent particle size distributions for aerosol coagulation and droplet coalescence is developed. The technique is based upon a bin-wise sectionalization of the particle mass domain and by imposing the condition of mass conservation for each component. The distribution of each species as a function of the total particle mass is represented in each mass bin as a two-parameter exponential function. Particles of a given mass are assumed to be internally homogeneously mixed. The method is shown to be numerically stable for a wide range of time steps. The numerical solution is compared with both analytical result…
Experimental analysis of bubble size distributions in 2D gas fluidized beds
2010
Abstract The present work focuses on the development of a novel statistical approach for the analysis of the behavior of a 2D fluidized bed operating under bubbling and slugging conditions. Experimental data were collected by means of a purposely built lab-scale 2D fluidized bed and an original digital image analysis technique (DIAT), allowing the acquisition of a number of data sufficient to perform a statistical analysis of bubble dynamics. In particular, measurements of bubble size distributions (BSD) along the bed were performed. The analysis allowed to characterize the shape of BSD for different particle systems and fluidization gas velocities; interestingly a bimodal shape of BSD is o…
Statistical mechanics of fullerene coalescence growth
2006
Among the different carbon allotropes fullerenes are exceptionally intriguing for their spheroidal topology out of pentagons and hexagons. However, the dominant formation mode is still ambiguous. Here, we analyze the fullerene formation process by the statistical analysis of fullerene sizes produced in a laser-induced microplasma finding that a simple two-parameter lognormal distribution describes impressively well the cluster frequencies under various conditions. Our findings clearly reveal coalescent growth following a classical collision dynamics and disagree with several earlier assumptions.
Parental Stress and ASD
2016
The objectives of this study were (a) to evaluate parental stress in parents of children with autism spectrum disorders (ASD group) and compare it with the stress in parents of children with typical development (comparison group); (b) to study the relationship between parental stress, autism severity, and both verbal and performance IQ; and (c) to study the relationship between parental stress and resilience. Parental stress in the ASD group was clinically significant and higher than in the comparison group. The child’s autism severity was a significant predictor of parental stress related to the child’s distractibility and hyperactivity. The child’s verbal IQ was a significant predictor o…
Channel selection in Cognitive Radio Networks: A Switchable Bayesian Learning Automata approach
2013
We consider the problem of a user operating within a Cognitive Radio Network (CRN) which involves N channels each associated with a Primary User (PU). The problem consists of allocating a channel which, at any given time instant is not being used by a PU, to a Secondary User (SU). Within our study, we assume that a SU is allowed to perform “channel switching”, i.e., to choose an alternate channel S times (where S +1 ≤ N) if the previous choice does not lead to a channel which is vacant. The paper first presents a formal probabilistic model for the problem itself, referred to as the Formal Secondary Channel Selection (FSCS) problem, and the characteristics of the FSCS are then analyzed. Ther…