1,721,054 research outputs found
Statistical inference on accumulation curves for inventorying forest diversity: a design-based critical look
No full textStatistical inference on accumulation curves is considered from a design-based perspective. Preliminaries on probabilistic sampling of plants and species are given, emphasizing the fundamental role of independent replications of the sampling scheme. The role of rarefaction curves as a tool for making inference on the effectiveness of the sampling procedures to compile accurate species lists is outlined. Design-based and model-based inference are discussed and compared. Some future developments for design-based inference are considered
Editorial: Inference on biological populations
No full textDesigning an unreplicated field trial essentially involves firstly selecting the plots for the check varieties, and secondly arranging the check varieties among these plots. Selecting the check plots appears to be very similar to choosing sites for a monitoring network, or choosing sites in a region at which to take a sample. The problems appear to be even closer if spatial dependence is postulated, when another aim in choosing the sites is to allow efficient estimation of the dependence. In this paper, the designs of monitoring networks and spatial samples, and some related design problems, are considered to see if they have implications for the design of unreplicated field trials. Copyright © 2001 John Wiley & Sons, Ltd
Applying the Horvitz-Thompson criterion in complex designs: a computer-intensive perspective for estimating inclusion probabilities
No full textA modification of the Horvitz–Thompson estimator is proposed for complex sampling designs. The inclusion
probabilities are estimated by means of independent replications of the sampling scheme. The properties of
the resulting estimator are derived. Guidelines for choosing the appropriate number of replications are given
and some applications are considered
An adaptive algorithm for estimating inclusion probabilities and performing the Horvitz–Thompson criterion in complex designs
No full textComplex sampling schemes, Horvitz-Thomson estimation, Replications, Empirical inclusion probabilities, Bennet inequality,
Kernel estimators of probability density functions by ranked-set sampling
No full textKernel estimation of probability density functions is considered when ranked-set samples are available. The properties of the resulting estimators are derived for small and large samples, while performance with respect to the usual simple random sample estimators is investigated for a range of probability density models. Copyright © 2002 by Marcel Dekker, Inc
Assessing Multivariate Normality on the "Worst" Sample Configuration
No full textA rotation procedure searching for the worst sample configuration is proposed when the hypothesis of multivariate normality is assessed by evaluating the univariate normality of each row of the scaled residual matrix.This procedure gives rise to multivariate normality test statistics which are invariant with respect to linear non-singular transformations of the sample data. An empirical power study with respect to selected alternative distributions demonstrates how the worst rotation procedure performs better than the rotation procedure proposed by Szkutnik
Area-based lidar-assisted estimation of forest standing volume
No full textAirborne laser scanning (lidar) technology is increasingly being applied in forest ecosystem surveys. This research note proposes a design-based approach for the lidar-assisted estimation of forest standing volume when ground surveys are performed by means of fixed-area plots. The lidar measurement of the height of the upper canopy (digital crown model) is performed for the whole study area, and the resulting pixel heights are adopted as auxiliary information to couple with the standing volume acquired on the ground by means of sample plots. The ratio estimator for the total volume of the forest is derived in a complete design-based framework together with an unbiased estimator of its sampling variance and the corresponding confidence interval. The proposed procedure has been tested in Bosco della Fontana, a lowland forest in Northern Italy, obtaining a 95% confidence interval for the total volume, which is approximately 2/3 smaller than that obtained by solely using information arising from field plots
Statistical properties of abundance estimates based on line-intercept and network sampling of tracks
No full textLine-intercept sampling (Becker, 1991) and network sampling (Becker et al., 1998) seem to be the most appropriate procedures for estimating animal abundance in a study area on the basis of tracks. The purpose of this paper is to investigate the statistical properties of these alternative procedures by constructing confidence intervals for abundance and comparing the interval performances in terms of width and coverage. © Springer-Verlag 2002
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