Search results for "survey."
showing 10 items of 4020 documents
Uniform convergence and asymptotic confidence bands for model-assisted estimators of the mean of sampled functional data
2013
When the study variable is functional and storage capacities are limited or transmission costs are high, selecting with survey sampling techniques a small fraction of the observations is an interesting alternative to signal compression techniques, particularly when the goal is the estimation of simple quantities such as means or totals. We extend, in this functional framework, model-assisted estimators with linear regression models that can take account of auxiliary variables whose totals over the population are known. We first show, under weak hypotheses on the sampling design and the regularity of the trajectories, that the estimator of the mean function as well as its variance estimator …
Estimation of total electricity consumption curves by sampling in a finite population when some trajectories are partially unobserved
2019
International audience; Millions of smart meters that are able to collect individual load curves, that is, electricity consumption time series, of residential and business customers at fine scale time grids are now deployed by electricity companies all around the world. It may be complex and costly to transmit and exploit such a large quantity of information, therefore it can be relevant to use survey sampling techniques to estimate mean load curves of specific groups of customers. Data collection, like every mass process, may undergo technical problems at every point of the metering and collection chain resulting in missing values. We consider imputation approaches (linear interpolation, k…
Using Complex Surveys to Estimate theL1-Median of a Functional Variable: Application to Electricity Load Curves
2012
Mean proles are widely used as indicators of the electricity consumption habits of customers. Currently, Electricit e De France (EDF), estimates class load proles by using point-wise mean function. Unfortunately, it is well known that the mean is highly sensitive to the presence of outliers, such as one or more consumers with unusually high-levels of consumption. In this paper, we propose an alternative to the mean prole: the L1-median prole which is more robust. When dealing with large datasets of functional data (load curves for example), survey sampling approaches are useful for estimating the median prole and avoid storing all of the data. We propose here estimators of the median trajec…
Systematic handling of missing data in complex study designs : experiences from the Health 2000 and 2011 Surveys
2016
We present a systematic approach to the practical and comprehensive handling of missing data motivated by our experiences of analyzing longitudinal survey data. We consider the Health 2000 and 2011 Surveys (BRIF8901) where increased non-response and non-participation from 2000 to 2011 was a major issue. The model assumptions involved in the complex sampling design, repeated measurements design, non-participation mechanisms and associations are presented graphically using methodology previously defined as a causal model with design, i.e. a functional causal model extended with the study design. This tool forces the statistician to make the study design and the missing-data mechanism explicit…
Flexible latent trait aggregation to analyze employability after the Ph.D. in Italy
2015
The analysis of satisfaction, employability and economic perspectives after the Ph.D. in Italy has not received adequate attention in the past, especially in terms of comparison among universities. To analyze these aspects, in this paper we consider data from the survey ‘Statistica in TEma di Laureati e LAvoro’ on doctors who achieved the title on 2007, 2008 and 2009 [CILEA, Laureati STELLA, indagine occupazionale post-dottorato, dottori di ricerca 2007–2008, Tech. Rep., CILEA, Segrate, 2010; CILEA,Laureati STELLA, indagine occupazionale post-dottorato, dottori di ricerca 2008–2009, Tech. Rep., CILEA, Segrate, 2011]. To deal with the complex, multidimensional nature of the concept, we propo…
Analysis of Educational Frequency Data from a Complex Sample Survey
1991
Abstract Some recent methods are presented for analyzing categorial data from complex surveys involving clustering familiar in educational research where e.g. teaching groups are used as sample clusters. The methods are introduced through a discussion of the test of independence on a two‐way table and the analysis of a two‐way table using logistic regression models. The analyses are illustrated using data from the First National Assessment of the Finnish Comprehensive School 1979. The primary focus of the paper is on the methods that provide first‐order corrections to standard multinomial‐based chi‐square tests by taking account of survey design effects. Both first‐ and second‐order correct…
The cumulative effect of multiple dimensions of lifestyle on risky drinking during the Covid-19 pandemic
2021
Lifestyle impacts morbidity and mortality worldwide. Herein, we evaluated the association of a multidimensional lifestyle measure and its domains (diet/nutrition, substance use, physical activity, social, stress management, sleep, environmental exposure) with risky drinking. Also, we analyzed the cumulative effect of unhealthy domains in the likelihood of presenting risky drinking. To reach these objectives, data from a web survey conducted in Brazil and Spain was analyzed. The main outcome was risky drinking assessed by the AUDIT-C. Lifestyle was measured using the Short Multidimensional Inventory Lifestyle Evaluation (SMILE). Fixed logistic models were used to evaluate associations betwee…
Shaping the firm's external search strategy
2014
This paper explores the determinants of external knowledge search strategies, specifically, exploitative and exploratory search. The literature emphasizes environmental context and technological resources, especially R&D, as important determinants of the search strategy. In this paper we focus on two types of the firm's formal structure: formalized and decentralized structures. The study uses survey data from the ceramic tile industry in Spain. The results show that a competitive environment and a decentralized organizational structure play a role in shaping the firm's external search strategy, but that R&D has no effect. We find that competition inhibits exploratory search, while a decentr…
Bayesian Estimation of Political Transition Matrices
1994
A decision framework is used to propose a procedure designed to estimate the reallocation of the vote of each individual party between two consecutive political elections, given the results of the elections, the information provided by a sample survey, and some assumptions on the hierarchical structure of the population.
Burnout and Online Medical Education: Romanian Students in Lockdown and Their Residency Choices.
2022
The primary aim of the study was to investigate the prevalence of burnout in Romanian medical students during the COVID-19 pandemic using the Maslach Burnout Inventory-General Survey for Students (MBI-GS(S)). The presence of burnout was assessed based on Exhaustion (EX), Cynicism (CY) and Professional Efficacy (PE) subscales. The secondary aim of the study was to identify the presence of intentional shift in medical specialty compared to their initial pursued choice within the population investigated. Data was collected online at the end of 2020 and beginning of 2021 through a licensed, customized MBI-GS(S) questionnaire from a sample of 126 Romanian medical students at the two leading medi…