Statistical Modelling 4 (2004), 77–89
An empirical model for underdispersed count data
Martin S. Ridout
Institute of Mathematics and Statistics
University of Kent, Canterbury
Kent CT2 7NF
U.K.
email: M.S.Ridout@ukc.ac.uk
Panagiotis Besbeas
Institute of Mathematics and Statistics
University of Kent, Canterbury
Kent CT2 7NF
U.K.
Abstract:
We present a novel distribution for modelling count data that are
underdispersed relative to the Poisson distribution. The distribution
is a form of weighted Poisson distribution and is shown to have
advantages over other weighted Poisson distributions that have
been proposed to model underdispersion. One key difference is
that the weights in our distribution are centred on the mean
of the underlying Poisson distribution. Several illustrative
examples are presented that illustrate the consistently good
performance of the distribution.
Keywords:
Clutch size; exponential weighting; linnet; Poisson process;
polyspermy; weighted Poisson distribution
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