Search results for "Linear Model"
showing 10 items of 598 documents
Correlation of brain white matter diffusion anisotropy and mean diffusivity with reaction time in an oddball task.
2008
<i>Background:</i> Reaction time (RT) is a frequently used measure of information processing speed, but the underlying physiological and anatomical conditions are not yet fully understood. A correlation between measures of white matter (WM) ultrastructural properties and RT is expected – particularly for those WM tracts that are involved in the attentional system of the brain. <i>Methods:</i> Diffusion tensor imaging data were acquired in 43 unrelated healthy subjects (age: 22.7 ± 1.8 years), and RT was measured during an attention-requiring visual oddball task in the same scanning session. Voxel-by-voxel and region of interest analyses were performed for the large a…
Chocolate Consumption and Indicators of Adiposity in US Adults.
2020
International audience; Purpose: The purpose of this research is to investigate the association between consumption of chocolate and measures of adiposity in a large, representative sample of US adults. Methods: Cross-sectional data from 13,626 nondiabetic adults (≥20 years) participating in the National Health and Nutrition Examination Survey study were aggregated using 5 study cycles from 2005-2006 through 2013-2014. Chocolate consumption was determined based on 2 24-hour dietary recalls. Body mass index (BMI) and waist circumference were objectively measured. We used multivariable linear regression to test associations of 1) any chocolate consumption (yes/no), and 2) the total amount of …
Methods and Tools for Bayesian Variable Selection and Model Averaging in Normal Linear Regression
2018
In this paper, we briefly review the main methodological aspects concerned with the application of the Bayesian approach to model choice and model averaging in the context of variable selection in regression models. This includes prior elicitation, summaries of the posterior distribution and computational strategies. We then examine and compare various publicly available R-packages, summarizing and explaining the differences between packages and giving recommendations for applied users. We find that all packages reviewed (can) lead to very similar results, but there are potentially important differences in flexibility and efficiency of the packages.
Desigualdades y mortalidad por cirrosis en varones (Zaragoza, 1996-2003)
2011
ResumenObjetivosAnalizar diferencias geográficas en la mortalidad por cirrosis hepática, en varones, en la provincia de Zaragoza, y su posible asociación con indicadores socioeconómicos, así como identificar la adecuación, en el ámbito rural, del índice de privación del proyecto MEDEA.MétodosLa unidad geográfica de análisis para Zaragoza capital fue la sección censal, y para el resto de la provincia el municipio. Para cada unidad de análisis se calculó la razón de mortalidad estandarizada cruda y suavizada mediante un modelo lineal generalizado mixto bayesiano. Se calculó un índice sintético de privación y se incluyó en el modelo en cuartiles. También se realizó el análisis exploratorio inc…
Age-related satisfaction with complete dentures, desire for improvement and attitudes to implant treatment
1994
In the edentulous lower jaw implant stabilised dentures have proved clinically so successful that the indication for this treatment is now being discussed more often with geriatric patients. The aim of this study of edentate subjects was to determine the age-relation of the demand for denture improvement, the risks and feasibility of implant treatment. Sixty four complete denture wearers aged from 42 to 84 years took part in the study. A questionnaire was used to determine the subjective demand for denture improvement. For 33 subjects implants seemed possible. For these patients fear and scepticism concerning implant treatment were specified and quantified. Impaired general health was the m…
Weighted-Average Least Squares (WALS): Confidence and Prediction Intervals
2022
We extend the results of De Luca et al. (2021) to inference for linear regression models based on weighted-average least squares (WALS), a frequentist model averaging approach with a Bayesian flavor. We concentrate on inference about a single focus parameter, interpreted as the causal effect of a policy or intervention, in the presence of a potentially large number of auxiliary parameters representing the nuisance component of the model. In our Monte Carlo simulations we compare the performance of WALS with that of several competing estimators, including the unrestricted least-squares estimator (with all auxiliary regressors) and the restricted least-squares estimator (with no auxiliary reg…
Visualizing the flow of evidence in network meta-analysis and characterizing mixed treatment comparisons
2013
Network meta-analysis techniques allow for pooling evidence from different studies with only partially overlapping designs for getting a broader basis for decision support. The results are network-based effect estimates that take indirect evidence into account for all pairs of treatments. The results critically depend on homogeneity and consistency assumptions, which are sometimes difficult to investigate. To support such evaluation, we propose a display of the flow of evidence and introduce new measures that characterize the structure of a mixed treatment comparison. Specifically, a linear fixed effects model for network meta-analysis is considered, where the network estimates for two trea…
Methods to Use Big Wearable Heart Rate Data for Estimation of Physical Activity in Population Level
2015
Technologies for wearable health monitoring are becoming increasingly popular and affordable. As a result, large-scale health databases from a large number of individuals are becoming available. However, analysis of these databases requires special methodology to transform available parameters into more generic ones and to manage such non-balanced data characteristics as biases and sampling issues. In this paper, we introduce a methodology for studying physical activity from big wearable heart rate (HR) data on about 5 000 working-age individuals, each measured only for a few days. Physical activity was assessed by oxygen consumption (VO2) calculated from measured HR data using a neural net…
Morphological parameters as predictors of successful correction of Class III malocclusion
2001
The aim of the study was to assess pre-treatment cephalometric parameters and measurements of the size of the apical bases as predictors of successful orthodontic correction of Class III malocclusions. Pre- and post-treatment lateral cephalograms and study models of 80 completed Class III subjects were examined to obtain 23 cephalometric parameters taken mainly from the analyses of McNamara and Schwarz, and to measure the size of the apical bases. Success of occlusal correction was evaluated as the percentage change of peer assessment rating score during treatment, which was used as the dependent variable in multivariate statistical analyses testing the predictive value of the parameters as…
Phenological and intrinsic predictors of mite and haemacoccidian infection dynamics in a Mediterranean community of lizards
2021
Ectotherms are vulnerable to environmental changes and their parasites are biological health indicators. Thus, parasite load in ectotherms is expected to show a marked phenology. This study investigates temporal host–parasite dynamics in a lizard community in Eastern Spain during an entire annual activity period. The hosts investigated were Acanthodactylus erythrurus, Psammodromus algirus and Psammodromus edwardsianus, three lizard species coexisting in a mixed habitat of forests and dunes, providing a range of body sizes, ecological requirements and life history traits. Habitat and climate were considered as potential environmental predictors of parasite abundance, while size, body conditi…