Presenting summaries of plant density data that are meaningful to your readers — a case for giving the median as well as the mean
CSIRO Sustainable Ecosystems, St Lucia, Queensland, Australia Abstract
The distribution of plant density counts is sometimes
highly skewed and presenting only the
mean can give a misleading impression of the
pasture as a whole, but indications of skewness
or dispersion are rarely given in the literature.
To evaluate this, 89 data sets from field experiments
were analysed to examine the relationship
between the mean plant density, the median plant
density, and simple measures of skewness and
dispersion. In new sowings, the mean seedling
density, whether sown by hand in small plots or
by machine in larger plots, was consistently close
to the median density. In established pastures, the
mean:median ratio was <1.5 in approximately
half of the 39 analyses undertaken but was more
than 2 in about one-quarter of the analyses, |