Search results for "sampling"

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…

Contaminant Intrusion through Leaks in Water Distribution System: Experimental Analysis

2015

Abstract This paper presents the results of experimental tests on the intrusion of contaminant through pipe cracks in water distribution network resulting from low/negative pressures. The tests were carried out on a looped distribution network at the University of Enna and were performed first producing a pressure transient that causes negative pressures then reproducing intermittent supply. A soluble contaminant was added to the water volume in the network through a pipe crack. Sampling of water volume was carried out in two nodes of the network and the contaminant concentrations were measured. It was showed that: the contaminant was drawn in and transported, in the first set of tests; the…

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.

Intraductal aspiration: a promising new tissue-sampling technique for the diagnosis of suspected malignant biliary strictures

2012

Brushing is the most commonly used technique for biliary sampling at ERCP, despite its limited sensitivity. To evaluate intraductal aspiration (IDA) as a new combined endoscopic technique for cytodiagnosis, its cellular adequacy, diagnostic accuracy for cancer detection, feasibility, and safety. Prospective, observational study. Single tertiary referral center. IDA cellular adequacy, diagnostic accuracy for cancer detection, feasibility, and safety. From April 2009 to September 2010, 42 consecutive patients with suspected malignant biliary stricture underwent ERCP, with tissue sampling obtained with IDA. IDA included performance of standard brushing in all patients. After standard brushing,…

Reassessing the evidence for tree-growth and inferred temperature change during the Common Era in Yamalia, northwest Siberia

2013

AbstractThe development of research into the history of tree growth and inferred summer temperature changes in Yamalia spanning the last 2000 years is reviewed. One focus is the evolving production of tree-ring width (TRW) and tree-ring maximum-latewood density (MXD) larch (Larix sibirica) chronologies, incorporating different applications of Regional Curve Standardisation (RCS). Another focus is the comparison of independent data representing past tree growth in adjacent Yamalia areas: Yamal and Polar Urals, and the examination of the evidence for common growth behaviour at different timescales. The sample data we use are far more numerous and cover a longer time-span at Yamal compared to …

100-millisecond Resolution for Accurate Overirradiance Measurements

2013

Cloud enhancement of sunlight results in peak irradiance well exceeding extraterrestrial levels, even at high latitudes. Values above 1.8 kW/m2 are possible in the equatorial regions. Recently, we detected bursts over 1.5 kW/m2 in Northern Europe at latitude close to 60°N. Overirradiance events (intensities much higher than 1 sun) can last tens of minutes, as well as less than 1 s. They may have caused series arcing in photovoltaic modules, leading to fires and loss of property. The accurate measurement of short bursts requires sensors with response times on the order of milliseconds. The long response times of thermopile pyranometers smooth out important details of very short-lived peaks a…

Reaction coordinates and transition states in enzymatic catalysis

2017

Enzymatic reactions are complex chemical processes taking place in complex dynamic environments. Theoretical characterization of these reactions requires the determination of the reaction coordinate and the transition state ensemble. This is not an easy task because many degrees of freedom may be involved in principle. We present recent efforts to find good enzymatic reaction coordinates and the implications of these findings in the interpretation of enzymatic efficiency. In particular, we analyze different strategies based on the use of minimum free energy paths and direct localization of the dividing surface on multidimensional free energy surfaces. Another strategy is based on the genera…

A Successive Umbrella Sampling Algorithm to Sample and Overcome Free Energy Barriers

2006

Improving predictive accuracy of exit polls

2010

Abstract Exit polls are best known for their use in election forecasting. In recent years, however, some prominent mistaken predictions have been made, undermining public confidence in the accuracy of both exit polls and survey methods. Nonresponse bias has been claimed as being one of the main reasons for inaccurate projections. Traditionally, the issue has been handled through an age–race–sex adjustment at the national and state levels. An alternative solution is suggested and detailed in this paper. A two-step strategy is proposed to reduce nonresponse bias and improve predictions. First, “vote-remembering” (vote recall) is used to correct party proportion estimates at polling locations;…

AN EMPIRICAL STUDY OF LATVIAN CONSUMER’S ATTITUDES AND PERCEPTIONS TOWARDS GENETICALLY MODIFIED ORGANISMS

2016

Genetic modification and genetically modified organisms (GMO) remains a controversial issue. Latvian consumers’ attitude towards genetic modification and GMO have been characterized as negative using Eurobarometer data, but so far no specific investigation of Latvian consumers has been done in this field. The aim of this study was to analyse Latvian consumers’ attitude towards genetic modification and GMO, the subjective and objective knowledge about this questions and acceptability of use of GMO in different application areas. Main task in frame of this research is to summarize different literature and data available to outline some of factors that influence attitudes towards GMO: mainly p…