Difference between revisions of "Documentation/How Tos/Calc: BETADIST function"
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: The beta distribution is a family of continuous probability distributions, defined for an interval <tt>'''a'''</tt> to <tt>'''b'''</tt>, where <tt>'''α'''</tt> and <tt>'''β'''</tt> are parameters controlling the shape of the distribution. <tt>'''n'''</tt> lies between <tt>'''a'''</tt> and <tt>'''b'''</tt>. | : The beta distribution is a family of continuous probability distributions, defined for an interval <tt>'''a'''</tt> to <tt>'''b'''</tt>, where <tt>'''α'''</tt> and <tt>'''β'''</tt> are parameters controlling the shape of the distribution. <tt>'''n'''</tt> lies between <tt>'''a'''</tt> and <tt>'''b'''</tt>. | ||
− | : <tt>'''BETADIST'''</tt> calculates the (cumulative) distribution function ''F''(<tt>'''x'''</tt>;<tt>'''α'''</tt>, <tt>'''β'''</tt>) = ''I''<tt>'''<sub>x</sub>'''</tt>(<tt>'''α'''</tt>, <tt>'''β'''</tt>) where <tt>'''x'''</tt> = (<tt>'''n'''</tt>-<tt>'''a'''</tt>)/(<tt>'''b'''</tt>-<tt>'''a'''</tt>) and ''I''<tt>'''<sub>x</sub>'''</tt>(<tt>'''α'''</tt>, <tt>'''β'''</tt>) is the regularised incomplete beta function. | + | : <tt>'''BETADIST'''</tt> calculates the (cumulative) distribution function ''F''(<tt>'''x'''</tt>; <tt>'''α'''</tt>, <tt>'''β'''</tt>) = ''I''<tt>'''<sub>x</sub>'''</tt>(<tt>'''α'''</tt>, <tt>'''β'''</tt>) where <tt>'''x'''</tt> = (<tt>'''n'''</tt>-<tt>'''a'''</tt>)/(<tt>'''b'''</tt>-<tt>'''a'''</tt>) and ''I''<tt>'''<sub>x</sub>'''</tt>(<tt>'''α'''</tt>, <tt>'''β'''</tt>) is the regularised incomplete beta function. |
− | : <tt>'''a'''</tt> and <tt>'''b'''</tt> are optional parameters which default (if omitted) to <tt>'''0'''</tt> and <tt>'''1'''</tt>. | + | : <tt>'''a'''</tt> and <tt>'''b'''</tt> are optional parameters which default (if omitted) to <tt>'''0'''</tt> and <tt>'''1'''</tt>. |
=== Example: === | === Example: === |
Revision as of 06:17, 26 April 2008
BETADIST
Calcualates the (cumulative) distribution function of the beta distribution.
Syntax:
BETADIST(n; α; β; a; b)
- The beta distribution is a family of continuous probability distributions, defined for an interval a to b, where α and β are parameters controlling the shape of the distribution. n lies between a and b.
- BETADIST calculates the (cumulative) distribution function F(x; α, β) = Ix(α, β) where x = (n-a)/(b-a) and Ix(α, β) is the regularised incomplete beta function.
- a and b are optional parameters which default (if omitted) to 0 and 1.
Example:
BETADIST(0.75; 3; 4)
- returns approximately 0.96.