Difference between revisions of "Documentation/How Tos/Calc: CHISQDIST function"
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Revision as of 12:00, 17 May 2010
This function is not yet implemented but expected for OpenOffice.org version 3.1.
CHISQDIST
Calculates values for a χ^{2}distribution.
Syntax
CHISQDIST(x; k; Cumulative)
 x is the number, at which you will evaluate the χ^{2}distribution.
 k sets the degrees of freedom for the χ^{2}distribution
 Constraint: k must be a positive integer
 Cumulative is a logical value.
 In the case Cumulative=TRUE() the cumulative distribution function is used, in the case Cumulative=FALSE() the probability density function. This parameter is optional. It is set to TRUE() if missing.
Semantic
CHISQDIST(x;k;FALSE()) returns values of the probability density function for the χ^{2}distribution:
CHISQDIST(x;k;TRUE()) returns the left tail probability for the χ^{2}distribution:
Example
CHISQDIST(2.3;15;FALSE())
CHISQDIST(2.3;2;FALSE())

CHISQDIST(1.5;2;TRUE())
other valid call: CHISQDIST(1.5;2) 
CHISQDIST(18;15;TRUE())

Remarks
If you need CHISQDIST(x;k;TRUE()) with a non integer parameter k, then use GAMMADIST(x;k/2;2) instead.
For to get the right tail for large values x, do not calculate 1 − CHISQDIST. It is less accurate in those cases than using CHIDIST. CHISQDIST(x;k;TRUE()) + CHIDIST(x;k) = 1.
In the density case the internal calculation uses logarithmic and exponential function, if x >1425 or x · k > 1391000. The results are less accurate in those cases.
Issues
This function is not available in version 3.0 and earlier.