Search results for "sampling"

Sample design and weighting strategies in SHARE Wave 5

2015

This chapter provides a description of the sampling design and weighting strategies adopted in the fifth wave of SHARE. We begin by defining the target population that SHARE aims to represent. Next, we describe the sampling design focusing on the basic principles guiding the construction of the SHARE sample, the role played by sampling frames for coverage of the target population, and other important aspects of sampling - such as stratification, clustering and variation in selection probabilities - that affect the efficiency of sample-based inference. The chapter concludes with a description of the weighting strategies adopted by SHARE to handle problems of unit nonresponse in the baseline …

Data Quality in Tourism. Non-Sampling Errors in the Aeolian Islands Research.

2013

A Proposal to estimate the roaming–dog Total in an urban area through a PPSWOR spatial sampling with sample size greater than two

2018

Survey, tourism

2015

A survey is any organized and methodical activity that directly collects information on motivations, opinions, and behaviors about the characteristics of a given population, including tourists and residents of a destination. This article provides a description of the stages required when implementing a survey, for the Encyclopedia of Tourism, placing peculiar attention to the context of tourism.

Errors within web-based surveys: a comparison between two different tools for the analysis of tourist destinations websites quality

2011

Comparison of sampling methods and habitat types for detecting impacts on lake littoral macroinvertebrate assemblages along a gradient of human distu…

2010

We explored environmental variables structuring littoral macroinvertebrate communities in a large lake basin along a gradient of nutrient enrichment. Furthermore, we evaluated sensitivity and cost-effi ciency of different sampling schemes (i.e. combinations of three habitat types and a number of standard sampling methods) to detect changes in macroinvertebrate communities along this anthropogenic disturbance gradient. Partial canonical ordination analysis showed that habitat characteristics accounted for a major part (56 % uniquely) of the explained variation in the species composition of invertebrate communities. When different mesohabitats were examined separately, assemblage variation of…

Sampling procedure in a willow plantation for chemical elements important for biomass combustion quality

2015

Willow (Salix spp.) is expected to contribute significantly to the woody bioenergy system in the future, so more information on how to sample the quality of the willow biomass is needed. The objectives of this study were to investigate the spatial variation of elements within shoots of a willow clone ‘Tordis’, and to reveal the relationship between sampling position, shoot diameters, and distribution of elements. Five Tordis willow shoots were cut into 10–50 cm sections from base to top. The ash content and concentration of twelve elements (Al, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, Si, and Zn) in each section were determined. The results showed large spatial variation in the distribution of mos…

Weighted-Average Least Squares (WALS): Confidence and Prediction Intervals

2022

We extend the results of De Luca et al. (2021) to inference for linear regression models based on weighted-average least squares (WALS), a frequentist model averaging approach with a Bayesian flavor. We concentrate on inference about a single focus parameter, interpreted as the causal effect of a policy or intervention, in the presence of a potentially large number of auxiliary parameters representing the nuisance component of the model. In our Monte Carlo simulations we compare the performance of WALS with that of several competing estimators, including the unrestricted least-squares estimator (with all auxiliary regressors) and the restricted least-squares estimator (with no auxiliary reg…

Statistical Learning for End-to-End Simulations

2018

End-to-end mission performance simulators (E2ES) are suitable tools to accelerate satellite mission development from concet to deployment. One core element of these E2ES is the generation of synthetic scenes that are observed by the various instruments of an Earth Observation mission. The generation of these scenes rely on Radiative Transfer Models (RTM) for the simulation of light interaction with the Earth surface and atmosphere. However, the execution of advanced RTMs is impractical due to their large computation burden. Classical interpolation and statistical emulation methods of pre-computed Look-Up Tables (LUT) are therefore common practice to generate synthetic scenes in a reasonable…

Active Learning Methods for Efficient Hybrid Biophysical Variable Retrieval

2016

Kernel-based machine learning regression algorithms (MLRAs) are potentially powerful methods for being implemented into operational biophysical variable retrieval schemes. However, they face difficulties in coping with large training data sets. With the increasing amount of optical remote sensing data made available for analysis and the possibility of using a large amount of simulated data from radiative transfer models (RTMs) to train kernel MLRAs, efficient data reduction techniques will need to be implemented. Active learning (AL) methods enable to select the most informative samples in a data set. This letter introduces six AL methods for achieving optimized biophysical variable estimat…