Evaluation of analytical procedures for density estimation from line transect data — data grouping, data truncation and the unit of analysis. Southwell, C. & Weaver, K. Wildlife Research, 20:433–444, 1993. abstract bibtex Examined three aspects of line-transect analytical procedures: data grouping, data truncation and the use of individuals or clusters as the analytical unit. Bias and precision of density estimation in relation to various levels of these factors were assessed for four types of line-transect estimator (simple parametric, generalised parametric, non-parametric and quasi-strip) using line-transect survey data from macropod populations of known density. Bias was stable across all grouping levels tested for the simple parametric estimator, and stable across all but the coarsest grouping level for the generalized parametric and non-parametric estimators, but varied substantially across the range of levels tested for the quasi-strip estimator. Precision improved as the number of grouping levels increased for all estimators tested, but the extent of improvement varied between estimators, and for the estimator most affected, improvement was marginal beyond intermediate grouping levels. Density estimates were generally more accurate and precise when analysed in ungrouped form than in grouped form. Varying the analytical unit did not affect bias, but precision was significantly lower for cluster analysis than individual analysis for all estimators.
@ARTICLE{SouWea93,
author = {Southwell, C. and Weaver, K.},
title = {Evaluation of analytical procedures for density estimation from line
transect data --- data grouping, data truncation and the unit of
analysis},
journal = {Wildlife Research},
year = {1993},
volume = {20},
pages = {433--444},
abstract = {Examined three aspects of line-transect analytical procedures: data
grouping, data truncation and the use of individuals or clusters
as the analytical unit. Bias and precision of density estimation
in relation to various levels of these factors were assessed for
four types of line-transect estimator (simple parametric, generalised
parametric, non-parametric and quasi-strip) using line-transect survey
data from macropod populations of known density. Bias was stable
across all grouping levels tested for the simple parametric estimator,
and stable across all but the coarsest grouping level for the generalized
parametric and non-parametric estimators, but varied substantially
across the range of levels tested for the quasi-strip estimator.
Precision improved as the number of grouping levels increased for
all estimators tested, but the extent of improvement varied between
estimators, and for the estimator most affected, improvement was
marginal beyond intermediate grouping levels. Density estimates were
generally more accurate and precise when analysed in ungrouped form
than in grouped form. Varying the analytical unit did not affect
bias, but precision was significantly lower for cluster analysis
than individual analysis for all estimators.},
subdatabase = {distance}
}
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