Search results for "longitudinal"
showing 10 items of 1501 documents
Bayesian subcohort selection for longitudinal covariate measurements in follow‐up studies
2022
We propose an approach for the planning of longitudinal covariate measurements in follow-up studies where covariates are time-varying. We assume that the entire cohort cannot be selected for longitudinal measurements due to financial limitations, and study how a subset of the cohort should be selected optimally, in order to obtain precise estimates of covariate effects in a survival model. In our approach, the study will be designed sequentially utilizing the data collected in previous measurements of the individuals as prior information. We propose using a Bayesian optimality criterion in the subcohort selections, which is compared with simple random sampling using simulated and real follo…
Combining the intensity and sequencing of the poverty experience:a class of longitudinal poverty indices
2011
Summary Traditional measures of the persistence of poverty do not devote enough attention to the sequence of spells of poverty. We propose a new class of indices which measures the severity of chronic poverty, taking into account the way in which spells of poverty and non-poverty follow one another along individual life courses. All the years spent in poverty concur with the measurement of the persistency of poverty, albeit with a decreasing contribution provided that the distance between two consecutive spells of poverty becomes longer. Moreover, the distance from the poverty line and the poverty persistence probabilities are explicitly taken into account. A macrolevel index, which allows …
Generalized Symmetry Models for Hypercubic Concordance Tables
2000
Summary Frequency data obtained classifying a sample of 'units' by the same categorical variable repeatedly over 'components', can be arranged in a hypercubic concordance table (h.c.t.). This kind of data naturally arises in a number of different areas such as longitudinal studies, studies using matched and clustered data, item-response analysis, agreement analysis. In spite of the substantial diversity of the mechanisms that can generate them, data arranged in a h.c.t. can all be analyzed via models of symmetry and quasi-symmetry, which exploit the special structure of the h.c.t. The paper extends the definition of such models to any dimension, introducing the class of generalized symmetry…
Segmented mixed models with random changepoints: a maximum likelihood approach with application to treatment for depression study
2014
We present a simple and effective iterative procedure to estimate segmented mixed models in a likelihood based framework. Random effects and covariates are allowed for each model parameter, including the changepoint. The method is practical and avoids the computational burdens related to estimation of nonlinear mixed effects models. A conventional linear mixed model with proper covariates that account for the changepoints is the key to our estimating algorithm. We illustrate the method via simulations and using data from a randomized clinical trial focused on change in depressive symptoms over time which characteristically show two separate phases of change.
Degree course change and student performance: a mixed-effect approach
2015
This paper focuses on students credits earning speed over time and its determinants, dealing with the huge percentage of students who do not take the degree within the legal duration in the Italian University System. A new indicator for the performance of the student career is proposed on real data, concerning the cohort of students enrolled at a Faculty of the University of Palermo (followed for 7 years). The new indicator highlights a typical zero-inflated distribution and suggests to investigate the effect of the degree course (DC) change on the student career. A mixed-effect model for overdispersed data is considered, with the aim of taking into account the individual variability as wel…
Structural multilevel models for longitudinal mediation analysis: a definition variable approach
2022
Mediation analysis is used to assess the direct effect of an exposure on an outcome, and the indirect effect transmitted by a third intermediate variable. Longitudinal data are the most suited to address mediation, since they allow mediational effects to manifest over time. There exist several approaches to deal with longitudinal mediation analysis, and one of the most widely spread, especially in social and behavioural sciences, consists of using multilevel models. However, when applied to mediational settings, these models present some limitations that can be overcome moving to a structural perspective. In this paper we propose a new formalisation of multilevel models within a structural …
Networks as mediating variables: a Bayesian latent space approach
2022
AbstractThe use of network analysis to investigate social structures has recently seen a rise due to the high availability of data and the numerous insights it can provide into different fields. Most analyses focus on the topological characteristics of networks and the estimation of relationships between the nodes. We adopt a different perspective by considering the whole network as a random variable conveying the effect of an exposure on a response. This point of view represents a classical mediation setting, where the interest lies in estimating the indirect effect, that is, the effect propagated through the mediating variable. We introduce a latent space model mapping the network into a …
Les nouvelles ségrégations scolaires et professionnelles : XVIIIes journées d'étude sur les données longitudinales dans l'analyse du marché du travai…
2011
Relief (échanges du CEREQ), n°34, mai 2011, enligne sur http://www.cereq.fr/index.php/content/download/1971/22647/file/relief34.pdf; Ségrégations scolaires et professionnelles sont les deux thèmes des 18èmes Journées d'études sur les données longitudinales dans l'analyse du marché du travail. Quatre types de ségrégations font l'objet des communications et structurent cet ouvrage : les ségrégations spatiales ou sociales, celles liées à la segmentation du marché du travail et les ségrégations de genre.
Long-term determinants of changes in television viewing time in adults : Prospective analyses from the Young Finns Study
2018
Purpose: The long‐term effects of sociodemographic and health characteristics on television viewing (TV) time changes have not been identified in adulthood. We aimed to examine the modifiable and non‐modifiable determinants of changes in TV‐time in young adults over 10 years.Methods: Participants (N = 2929) aged 24‐39 years were recruited between 2001 and 2011 from the Cardiovascular Risk in Young Finns Study. Data were collected using questionnaires and a medical examination. The determinants of changes in TV‐time were estimated using latent growth modeling for men and women separately.Results: For men, inverse associations with initial levels of TV‐time were observed for students becoming…
Dynamics between student vs. teacher perceptions of mathematics task-orientation and mathematics performance among adolescents
2017
This study examined the dynamics between perceptions of mathematics task-orientation and mathematics performance among Finnish adolescents over a period of two last years of secondary school. Task-orientation in math was assessed at the beginning of grade 8 and again at the end of grade 9 using both student and teacher-reports. At the same time points, students' mathematics performance was evaluated via standardized test. The cross-lagged associations of task-orientation and mathematics performance were examined taking account the possible impacts of general cognitive ability, technical reading skills, reading comprehension and gender. The results showed that a high level of mathematics per…