Complaint About Statistics Toolbox Documentation

This is addressed to whoever in MathWorks is in charge of their internet
help file for the Statistics Toolbox at:

http://www.mathworks.com/access/helpdesk/help/toolbox/stats/

In the descriptions of the 'chi2pdf' and 'chi2cdf' functions there are
currently two statements I object to.

The first, in reference to 'Y = chi2pdf(X,V)', states that, "the values
in X must lie on the interval [0 1]." Surely you must mean [0 inf].
There is a similar erroneous statement for 'P = chi2cdf(X,V)'. Chi-square
distributions are unbounded in the positive direction.

The second is the statement for 'Y = chi2pdf(X,V)' that, "the result, y,
is the probability that a single observation from a chi^2 distribution
with nu degrees of freedom will have value x." That is misleading. The
chi-square distribution is continuous, not discrete, so the probability of
having an exact value of x is zero. It should read something like "... y
is the probability density of observations in the neighborhood of the
value x."

Roger Stafford
.

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