Search results for " longitudinal data"
showing 8 items of 8 documents
A statistical monitoring approach for automotive on-board diagnostic systems
2007
The current generation of vehicle models are increasingly being equipped with on-board diagnostic (OBD) systems aimed at assessing the ‘state of health’ of important anti-pollution subsystems and components. In order to promptly diagnose and fix quality and reliability problems that may potentially affect such complex diagnostic systems, even during advanced development prior to mass production, some vehicle prototypes undergo a testing phase under realistic conditions of use (a mileage accumulation campaign). The aim of this work is to set up a statistical tool for improving the reliability of the OBD system by monitoring its operation during the mileage accumulation campaign of a new vehi…
Flexible modelling of serial correlation in GLMM
2008
Convergence analysis for hierarchical longitudinal data
2018
Abstract Convergence analysis is typically envisaged either from a macro or a micro perspective. However, empirical tests tend to ignore that the two levels are often “nested” in a hierarchy. Building on hierarchical growth curve modelling, we propose an approach to convergence analysis that allows contemporaneous inference on macro and micro-convergence. Compared to the classic linear convergence analysis, the suggested methodology provides a more flexible alternative to model heterogeneity and validate the results for possible Galton's fallacy. We illustrate the approach in two empirical examples, one considering convergence across European regions and countries and the other across Itali…
Analysing the mediating role of a network: a Bayesian latent space approach
2020
The use of network analysis for the investigation of social structures has recently seen a rise, due both to the high availability of data and to 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 point of view, 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 the estimation of the indirect effect, that is, the effect propagated through the mediating variable. We introduce a latent space model mappin…
Gender Inequalities and Social Sustainability. Can Modernization Diminish the Gender Gap in Political Knowledge?
2020
The gender gap in political knowledge is a classical problem of Western democracies. In the 21st century, political knowledge is still unequally distributed between men and women, as many cross-section studies have shown. This is an indicator of women’s disempowerment and the distance which remains to be covered to achieve an inclusive and sustainable society. Could public policies and gender equality laws change the situation? Using a longitudinal database in which 600,000 survey responses are analysed from 1996 to 2017, this case study of Spain aims to shed some light on this question. It combines sociological and political approaches in line with the development theory of the gender gap …
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…
A NEW INDEX OF POVERTY PERSISTENCE
2008
This paper proposes a new indicator of poverty persistence based on a synthesis of the temporal sequences of the years spent in poverty and non poverty, taking into account the order in which poverty spells follow each other. The index is a measure with cardinal properties and it allows not only the ranking of the individuals according to the duration of their poverty experience but also to measure the distance between any two individuals in the population. The index can be built up at individual level and it is also possible to have an aggregated index at any territorial level. Micro data from a longitudinal survey are needed.