------------------------------------------------------ URA 2055 ----------------
Author(s) :
THIOULOUSE J.,ROYET J.P.,PLOYE H.,HOULLIER F.
Evaluation of the Precision of Systematic Sampling : Nugget Effect
and Covariogram Modelling
Journal of Microscopy
Serial Number : 172, 1993, pp. 249-256
ISSN : 0022-2720
Key-Words :
STEREOLOGY,VOLUME ESTIMATION,SERIAL SECTIONS,SYSTEMATIC SAMPLING,
SAMPLING INTENSITY,SAMPLING PRECISION,REGIONALIZED VARIABLES,
NUGGET EFFECT,OLFACTORY BULB,RODENT,TRANSITIVE COVARIOGRAM,
MORPHOMETRIC ESTIMATIONS
Abstract Systematic sampling designs are widely used in stereology. When
an estimator of the total amount, Q, of the sampled variable is
evaluated by such a procedure, the coefficient of error can be
predicted by applying Matheron's theory of regionalized variables.
To evaluate the accuracy of the estimate of Q, it is necessary to
study the behaviour of the regionalized variable and to model its
covariogram. Histological data with a low short-range variability
and agronomic data with a pronounced nugget effect provided the
biological material for extreme case studies. Results show that
the short-range variability, if present, cannot be detected when
only small samples are available. An underestimation of the
coefficient of error is then to be expected. We propose several
models of the covariogram, which can be used to test for presence
of a nugget effect. If a nugget effect is present, these models
will provide better estimates of the coefficient of error. If
there is no nugget effect the simplified method of Gundersen and
Jensen (1987) can be used and will provide reliable estimates of
the coefficient of error.
E-Mail : thioulou@biomserv.univ-lyon1.fr
Laboratoire de Biometrie, Genetique et Biologie des Populations
(URA 2055) - Univ. C. Bernard LYON I - 69622 VILLEURBANNE CEDEX