Search results for "Random effect"
showing 10 items of 57 documents
An Ordinal Joint Model for Breast Cancer
2017
We propose a Bayesian joint model to analyze the association between longitudinal measurements of an ordinal marker and time to a relevant event. The longitudinal process is defined in terms of a proportional-odds cumulative logit model and the time-to-event process through a left-truncated Cox proportional hazards model with information of the longitudinal marker and baseline covariates. Both longitudinal and survival processes are connected by a common vector of random effects.
Healthcare costs of the SATisfaction and adherence to COPD treatment (SAT)study follow-up
2019
Abstract Background Chronic obstructive pulmonary disease (COPD) is characterised by recurring exacerbations. We estimated the costs of healthcare resources for COPD management funded by the Italian National Healthcare Service (INHS) for one year. Methods We examined the demographic, clinical, and economic variables at enrolment and follow-up visits (at 6 and 12 months) of COPD patients participating in the SAT study and referred to 20 Italian pulmonary centres with different institutional characteristics. Costs were expressed in Euro (€) 2018. A random effects log-linear panel regression model was performed to predict the average cost per patient. Results Most of the centres were public in…
COVID-19 y tabaquismo: revisión sistemática y metaanálisis de la evidencia
2021
RESUMEN Objetivo: el objetivo del estudio ha sido responder a las siguientes preguntas: ¿Se asocia el consumo de tabaco en pacientes con Covid-19 con una progresión negativa y desenlace adverso de la enfermedad? y, ¿se asocia el consumo de tabaco, actual y pasado, a una mayor posibilidad de desarrollar COVID-19? Material y Métodos: Se realizó una revisión sistemática (RS) y metaanálisis (MA) de trabajos publicados previamente. La estrategia de búsqueda incluyó todos los descriptores conocidos sobre Covid-19 y tabaco y se realizó en diferentes bases de datos. Se utilizaron modelos estadísticos adecuados para abordar el tamaño del efecto en un metaanálisis: modelo de efectos aleatorios y de e…
Bayesian hierarchical nonlinear modelling of intra-abdominal volume during pneumoperitoneum for laparoscopic surgery
2021
Laparoscopy is an operation carried out in the abdomen or pelvis through small incisions with external visual control by a camera. This technique needs the abdomen to be insufflated with carbon dioxide to obtain a working space for surgical instruments' manipulation. Identifying the critical point at which insufflation should be limited is crucial to maximizing surgical working space and minimizing injurious effects. Bayesian nonlinear growth mixed-effects models are applied to data coming from a repeated measures design. This study allows to assess the relationship between the insufflation pressure and the intra--abdominal volume.
Aspirin use and breast cancer risk: a meta-analysis and meta-regression of observational studies from 2001 to 2005
2007
Purpose To examine the recent epidemiological studies on aspirin use and breast cancer risk published from 2001 to 2005 within a meta-analysis, to investigate reasons for heterogeneity between the individual studies and to analyse a dose-response-relationship considering frequency and duration of use. Methods We systematically searched for cohort-studies and case-control-studies from 2001–2005, which evaluated the association between aspirin and breast cancer risk. We calculated a pooled estimate for the relative risk (RR) and investigated reasons for heterogeneity between the individual studies and analysed a dose-response-relationship using random effects mixed models. Results We identifi…
Meta-analysis of the relationship between teachers’ self-efficacy and attitudes toward inclusive education
2022
Abstract This meta-study aims to examine the size of the relationship between teachers' self-efficacy and attitudes toward inclusive education of K-12 students with special educational needs and to identify potential moderators (publication, sample, and research procedure characteristics). We synthesized the research conducted from 1994 to 2018, and 41 studies were included. Bare-bones meta-analysis with random effect model revealed a sample size weighted correlation coefficient between teachers’ self-efficacy and attitudes as r ¯ = 0.35 (CI = 0.31-0.39). The between-study variations were not associated with hypothesized publication and sample characteristics. However, the self-efficacy me…
Bayesian analysis and design for comparison of effect-sizes
2002
Comparison of effect-sizes, or more generally, of non-centrality parameters of non-central t distributions, is a common problem, especially in meta-analysis. The usual simplifying assumptions of either identical or non-related effect-sizes are often too restrictive to be appropriate. In this paper, the effect-sizes are modeled as random effects with t distributions. Bayesian hierarchical models are used both to design and analyze experiments. The main goal is to compare effect-sizes. Sample sizes are chosen so as to make accurate inferences about the difference of effect-sizes and also to convincingly solve the testing of equality of effect-sizes if such is the goal.
A model-based approach to Spotify data analysis: a Beta GLMM
2020
Digital music distribution is increasingly powered by automated mechanisms that continuously capture, sort and analyze large amounts of Web-based data. This paper deals with the management of songs audio features from a statistical point of view. In particular, it explores the data catching mechanisms enabled by Spotify Web API and suggests statistical tools for the analysis of these data. Special attention is devoted to songs popularity and a Beta model, including random effects, is proposed in order to give the first answer to questions like: which are the determinants of popularity? The identification of a model able to describe this relationship, the determination within the set of char…
Bayesian joint ordinal and survival modeling for breast cancer risk assessment
2016
We propose a joint model to analyze the structure and intensity of the association between longitudinal measurements of an ordinal marker and time to a relevant event. The longitudinal process is defined in terms of a proportional-odds cumulative logit model. Time-to-event is modeled through a left-truncated proportionalhazards model, which incorporates information of the longitudinal marker as well as baseline covariates. Both longitudinal and survival processes are connected by means of a common vector of random effects. General inferences are discussed under the Bayesian approach and include the posterior distribution of the probabilities associated to each longitudinal category and the …
Subject-specific odds ratios in binomial GLMMs with continuous response
2007
In a regression context, the dichotomization of a continuous outcome variable is often motivated by the need to express results in terms of the odds ratio, as a measure of association between the response and one or more risk factors. Starting from the recent work of Moser and Coombs (Odds ratios for a continuous outcome variable without dichotomizing, Statistics in Medicine, 2004, 23, 1843-1860), in this article we explore in a mixed model framework the possibility of obtaining odds ratio estimates from a regression linear model without the need of dichotomizing the response variable. It is shown that the odds ratio estimators derived from a linear mixed model outperform those from a binom…