chitest
Purpose
Uses chi-squared to test if sample has a specific
distribution.
Synopsis
vals = chitest(x,distname,classes)
Description
Assesses how well a particular distribution fits the data (x).
INPUTS:
x = The name of a matrix
(column vector) in which the sample data is stored.
distribution = Optional distribution name to
assume as the parent distribution for thesample. If this argument is missing,
then 'normal' is assumed. This argument must be in single quotes and the name
may be abbreviated.
classes = Optional argument naming the
number of equal probability intervals for which counts should be collected for
the test. If this argument is missing, then the number of classes is taken to
be

where {x} is the smallest
integer z such that z <= x. If
specified, the number of classes may not be greater than the length of the data
vector.
OUTPUTS:
The return value is a structure with fields:
chi2 = value
of the test statistic 
pval = p-value
associated with the test statistic
df = degrees
of freedom of the test
classes = number
of intervals for which counts are obtained
parameters = maximum
likelihood estimates
E = expected
counts for the classes
O = observed
counts for the classes
Note: If a sample contains all negative values,
then some of the overlay distributions will not be drawn as they are not
applicable. If only some of the sample is made up of negative values, these
values are ignored in obtaining the maximum likelihood estimates and subsequent
results.
Examples
chitest(x)
chitest(x,'exp')
chitest(x,'logistic',12)
See Also