Search results for " Sampling"

Estructura dimensional de las competencias del siglo XXI en los estudiantes universitarios de educación

2018

La nueva Sociedad del Conocimiento requiere nuevas competencias, que son conocidas como Competencias del siglo XXI. Estas competencias se subdividen en competencias de pensamiento y competencias de orden superior en tecnologías de información y comunicación. El objetivo de este artículo es determinar la estructura dimensional de las competencias del siglo XXI, junto con los factores personales clave en este sentido. Se trata de un estudio correlacional, basado en un diseño de encuesta, cuya muestra está constituida por estudiantes de los grados de Pedagogía y Educación Social de la Universidad de Valencia, seleccionados por muestreo no probabilístico y accidental, recogiendo la información …

Variance estimation and asymptotic confidence bands for the mean estimator of sampled functional data with high entropy unequal probability sampling …

2013

For fixed size sampling designs with high entropy it is well known that the variance of the Horvitz-Thompson estimator can be approximated by the H\'ajek formula. The interest of this asymptotic variance approximation is that it only involves the first order inclusion probabilities of the statistical units. We extend this variance formula when the variable under study is functional and we prove, under general conditions on the regularity of the individual trajectories and the sampling design, that we can get a uniformly convergent estimator of the variance function of the Horvitz-Thompson estimator of the mean function. Rates of convergence to the true variance function are given for the re…

Unpredictability of fish recruitment: interannual variation in young-of-the-year abundance

2000

In 1989-1998, vendace larvae Coregonus albula were sampled in Finnish lakes following a stratified random sampling design. The abundance of young-of-the-year vendace after the first growing season was estimated using catch-per-unit-effort statistics. The number or total area of nursery places hardly limited the recruitment of vendace in the study lakes. The major proportion of prerecruit mortality of vendace occurred in the larval phase and larval sampling produced significant information on young-of-the-year survival. Although larval abundances and recruitment were clearly associated only in Lake Onkamo, generally high larval abundance was needed to produce high number of recruits.

Robust estimation of mean electricity consumption curves by sampling for small areas in presence of missing values

2017

In this thesis, we address the problem of robust estimation of mean or total electricity consumption curves by sampling in a finite population for the entire population and for small areas. We are also interested in estimating mean curves by sampling in presence of partially missing trajectories.Indeed, many studies carried out in the French electricity company EDF, for marketing or power grid management purposes, are based on the analysis of mean or total electricity consumption curves at a fine time scale, for different groups of clients sharing some common characteristics.Because of privacy issues and financial costs, it is not possible to measure the electricity consumption curve of eac…

Slacking Off or Winding Down? An Experience Sampling Study on the Drivers and Consequences of Media Use for Recovery Versus Procrastination

2016

Today's constant availability of media content provides users with various recreational resources. It may also challenge self-control, however, once media exposure conflicts with other goals and obligations. How media users deal with these self-regulatory chances and risks in their daily lives is largely unknown. Our study addressed the predictors and consequences of recreational and procrastinatory media use using experience sampling methodology (N = 215; 1,094 media use episodes). Results suggest that trait (self-control, performance goal orientation) as well as state variables (exhaustion) are significant predictors of media use for recovery versus procrastination. Whereas recreational m…

Guide to Practical Work with the Monte Carlo Method

2002

The guide is structured such that we proceed from the “easy” simulation methods and algorithms to the more sophisticated. For each method the algorithms are presented by the technique of stepwise refinement. We first present the idea and the basic outline. From then on we proceed by breaking up the larger logical and algorithmic structures into smaller ones, until we have reached the level of single basic statements. Sometimes we may elect not to go to such a depth and the reader is asked to fill in the gaps.

Predicting the bioaccumulation of polyaromatic hydrocarbons and polychlorinated biphenyls in benthic animals in sediments

2016

There were two main objectives in this study. The first was to compare the accuracy of different prediction methods for the chemical concentrations of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the organism, based on the measured chemical concentrations existing in sediment dry matter or pore water. The predicted tissue concentrations were compared to the measured ones after 28-day laboratory test using oligochaeta worms (Lumbriculus variegatus). The second objective was to compare the bioaccumulation of PAHs and PCBs in the laboratory test with the in situ bioaccumulation of these compounds. Using the traditional organic carbon-water partitioning model, tissue…

Statistical models and inference for spatial point patterns with intensity-dependent marks

2009

Treating schistosomiasis among South African high school pupils in an endemic area, a qualitative study

2017

Abstract Background Schistosomiasis, a neglected tropical disease caused by parasites that infest open water sources such as rivers and dams may increase susceptibility to HIV. Mass-treatment with praziquantel tablets, recommended by the World Health Organization reduces the prevalence of schistosomiasis. The goal in endemic areas is 75% treatment participation in every treatment round (e.g. yearly). However, in rural Ugu district, KwaZulu-Natal, South-Africa there was low participation among pupils in a Department of Health Mass-Treatment Campaign for schistosomiasis. Methods Nested in a large study on schistosomiasis the study was conducted in 2012 over 4 months using qualitative methods …

May Measurement Month 2018: a pragmatic global screening campaign to raise awareness of blood pressure by the International Society of Hypertension.

2019

Abstract Aims Raised blood pressure (BP) is the biggest contributor to mortality and disease burden worldwide and fewer than half of those with hypertension are aware of it. May Measurement Month (MMM) is a global campaign set up in 2017, to raise awareness of high BP and as a pragmatic solution to a lack of formal screening worldwide. The 2018 campaign was expanded, aiming to include more participants and countries. Methods and results Eighty-nine countries participated in MMM 2018. Volunteers (≥18 years) were recruited through opportunistic sampling at a variety of screening sites. Each participant had three BP measurements and completed a questionnaire on demographic, lifestyle, and envi…