Seminari presso il DSS Udine

[Tommaso Proietti <proietti@dss.uniud.it>]

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SEMINARI PRESSO IL DIPARTIMENTO DI SCIENZE STATISTICHE
Saletta seminari
Via Treppo 18, UDINE  

1. -----------------------------------------------------------------

MARTEDI' 3 OTTOBRE, ORE 16.00

"Modelling relation between two variables in a designed experiment"

Ib Skovgaard,

The Royal Veterinary and Agricultural University, Denmark

Abstract. 
Quite often when experiments are carried out several responses are
measured on each individual. For example, the quality of a food product
could be measured by chemical analysis or by a taste panel of assessors,
or in plant science yield and amount of weed could be the two variables.
The experimenter will typically be interested in the relation between
the two variables without regard to treatments or replications. Quite
surprisingly no commonly known statistical models are suitable for this
common situation. In the talk the ultrastructural model (Dolby, 1976)
will be suggested and discussed, but problems of estimation and testing
are yet largely unsolved.

2. ------------------------------------------------------------------
MARTEDI' 10 OTTOBRE, ORE 15.30

"Ranked Survey Sampling Modeling"

Carlos N. Bouza

Departamento de Matemātica Aplicada
Facultad de Matemātica y Computaciōn
Universidad de La Habana, Cuba

Abstract
 
In different applications the statistician deals with the need  of
combining  control  and flexibility when surveying a population.  This is a
common problem in different studies.  For example if a  waste site is
studied the expert or decision maker [DM] is able to evaluate the randomly
selected different sampling sites and to establish a certain order by
evaluating subjectively the importance of each of them, by predicting the
value of the  variable of interest Y or by measuring a "cheap" one X.
Similar situation arises when a physician evaluates radiography results
device and ranks the  observed patterns (X) before deciding which patients
will constitute the sample to be evaluated by Axial Thomography.  To each
sampling unit a rank is assigned.  If m independent samples are selected,
by using Simple Random Sampling with replacement [SRSWR], and ranked using
X we can select the units taking into account the information given by the
ranks.  McIntyre [1952] proposed to use this information in the inference.
The method was named Ranked Set Sampling [RSS]. Recently this design has
been rediscovered and is generating a different alternative models. For
example See Patil et. al. [1994], Handbook of Statistics Vol. 12,  Stokes
[1995], Ann. Inst. Stat. Math., Kaur et. al. [1997], Biometrics, Samawi
[1996],  Muttlak [1998],  Bouza [submitted to] Biometrical Journal.
We  discuss the behavior of design based estimators of the population mean
m including the sample mean. Well known estimators are characterized:
ratio-type, difference , regression estimators.  They are compared in terms
of their accuracy.  The superpopulation approach is used as an alternative
and the solution  when non-responses are present is also studied.
Monte Carlo experiments permit to establish certain recommendations for
selecting the estimator to be used.
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La S.V. č invitata a partecipare.
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Tommaso Proietti                   
Dipartimento di Scienze Statistiche
Universitā di Udine
Via Treppo 18, 33100 Udine, Italy
Tel. +39 0432 24.9581
Fax  +39 0432 24.9595
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