[Forum SIS] Avviso di seminari - R. Benedetti (G. d’Annunzio University of Chieti-Pescara) and F. Piersimoni (ISTAT)

[Maria Giovanna Ranalli]

.: Prof. R. Benedetti, Dept. of Economics, G. d’Annunzio University of Chieti-Pescara
and F. Piersimoni, Agricultural Statistical Service, ISTAT :.

A Design for Spatial Finite Populations Based on the Within Sample Distance 

Friday, Nov. 16, 12:00
Dipartimento di Economia, Finanza e Statistica, Room 202
Università degli Studi di Perugia

Abstract
A method for selecting samples from a spatial finite population that are well spread over the population in every dimension, without the use of any spatial stratification is presented. The within sample distance matrix is summarized in a descriptive index which is used to define the probability p(s) of each sample to be selected. A set of units with higher within distance will be selected with higher probability than a set of nearby units. Through the standardization of the distance matrix the method can be used to produce equal and unequal probability samples either exact when a linear index is used to summarize the matrix or approximate when products and powers of the mean are used. The high flexibility of the selection algorithm can make possible numerous extensions to deal with some practical topics that are usually met in spatial surveys such as the sample coordination and the spread of units belonging to different domains. Some examples on real and simulated data show that the method gives estimates that are better than those obtained by using a classical solution as the Generalized Random Tessellation Stratified (GRTS) design and that often are even slightly better than those obtained by using recently proposed selection procedures as the Spatially Correlated Poisson Sampling (SCPS) and the Pivotal method. With respect to these distance based methods the proposed algorithm, even if in its nature it is computationally intensive, seems to be a faster solution particularly when dealing with large population frames.

Joint work with R. Chambers (Centre for Statistical and Survey Methodology, University of Wollongong, Australia)

Best regards

M. Giovanna Ranalli

~ Dipartimento di Economia, Finanza e Statistica
~ Sezione di Statistica
~ Via Pascoli
~ Universita' degli Studi di Perugia
~ 06123 Perugia - Italy

~ Tel +39 075 5855245
~ Fax +39 075 5855950
~ url: www.stat.unipg.it/~giovanna