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Subject: Re: [office-formula] BETADIST parameter Cumulative

On Fri, 2007-16-03 at 19:33 +0100, Eike Rathke wrote:
> Hi,
> Our definition of BETADIST currently has a 6th optional parameter
> Logical Cumulative = TRUE() that is not supported by any of the "usual"
> applications. If FALSE(), BETADIST is supposed to return the value of
> the probability density function. If TRUE(), the value of the cumulative
> distribution function, which is what applications do. Additionally it
> doesn't have the constraint a <= x <= b that applications have, and
> explicitly says so.
> Where did that originate from?
> I propose to remove that parameter and to add the constraint, otherwise
> the function would be incompatible with all applications, it seems.

argument (in XL, gnumeric,...) to switch between cumulative and
non-cumulative answers.

Is there any reasonable justification why other ...DIST functions do not
have the same switch (other than well XL picked that at random). It
would be easy to add this optional parameter to the programs.

Mathematically, the cumulative distribution and the density are defined
for all values of x, so there is no justification to have an constraint
such as a <= x <= b. The answer outside that range should just be 0 (or
1 in the case of cumulative if b < x).

The question is now mathematically correct the function definitions
should be.

Andreas J. Guelzow, Professor
Dept. of Mathematical & Computing Sciences
Concordia University College of Alberta

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