BETADIST Function

Basic Description

The Excel BETADIST function calculates the cumulative beta probability density function for a supplied set of parameters.

Syntax: BETADIST( x, alpha, beta, [A], [B] )

Where the function arguments are:

x The value at which the function is to be calculated (must be between [A] and [B])
alpha A parameter of the distribution (must be > 0)
beta A parameter of the distribution (must be > 0)
[A] An optional argument which gives the lower bound of the interval of x(if omitted, [A] takes the default value 0)
[B] An optional argument which gives the upper bound of the interval of x(if omitted, [B] takes the default value 1)

 

If the arguments [A] and [B] are set to 0 and 1 respectively, the function calculates the Standard Cumulative Beta Distribution.

Betadist Function Example

The chart on the right shows the Standard Cumulative Beta Distribution with the parameter alpha set to 4 and the parameter beta set to 5.

If you want to use Excel to calculate the value of this function at x = 0.4, this can be done with the Betadist function, as follows:

=BETADIST( 0.4, 4, 5 )

This gives the result 0.4059136.

Note that, in the above function call, the arguments [A] and [B] have been omitted, and so take on the default values 0 and 1 respectively. This is the Standard Cumulative Beta Distribution.

Plot of Standard Cumulative Beta Distribution with Alpha=4 and Beta=5Standard Cumulative Beta Distribution Function with α = 4 and β = 5

 

Trouble Shooting

If you get an error from the Excel Betadist function this is likely to be one of the following :

#NUM! Occurs if either the supplied x value is < [A] or > [B] or the supplied [A] and [B] arguments are equal the supplied alpha or the supplied beta argument is ≤ 0
#VALUE! Occurs if any of the supplied arguments are non-numeric

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