Parametric Test
Quadrat Analysis
Equations taken from Rogerson, 2001.
m
is the number of quadrats,
is the mean of the number of points per quadrat,
s
2
is the variance of the number of points per quadrat,
is the cell deviate, and
VMR
is the variancemean ratio.
Example:
The grid to the right has been drawn over a set of burglary
locations in a small urban area. Each dot represents one burglary. We
are interested in determining whether the burglaries are randomly
occurring within the urban area or if there is clustering. If there is a
large amount of variability in the frequency of points within cells,
then the data are clustering. Conversely, if the points are randomly
distributed, cell to cell variability would be minimal. Obviously the
choice of cell (quadrat) size is important, in that we do not want too
many cells having no observations. Although there is no rule as to
the number of observations each cell should have, somewhere
between 1 and 2 is usually sufficient. Cell deviates are the points per
cell minus the mean, squared… e.g. (01.17)
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 Summer '08
 Staff
 Addition, Standard Deviation, VMR

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