BETAINV

Returns the inverse of the cumulative beta probability distribution function. That is, if probability = BETADIST(x,...), then BETAINV(probability,...) = x. The cumulative beta distribution can be used in project planning to model probable completion times given an expected completion time and variability.

Syntax

BETAINV(probability,alpha,beta,A,B)

Probability    is a probability associated with the beta distribution.

Alpha    is a parameter to the distribution.

Beta    is a parameter to the distribution.

A    is an optional lower bound to the interval of x.

B    is an optional upper bound to the interval of x.

Remarks

• If any argument is nonnumeric, BETAINV returns the #VALUE! error value.
• If alpha ≤ 0 or beta ≤ 0, BETAINV returns the #NUM! error value.
• If probability ≤ 0 or probability > 1, BETAINV returns the #NUM! error value.
• If you omit values for A and B, BETAINV uses the standard cumulative beta distribution, so that A = 0 and B = 1.

BETAINV uses an iterative technique for calculating the function. Given a probability value, BETAINV iterates until the result is accurate to within ±3x10-7. If BETAINV does not converge after 100 iterations, the function returns the #N/A error value.

Example

Probability	Alpha	Beta	A	B	Formula	Description (Result)
0.685470581	8	10	1	3	=BETAINV([Probability],[Alpha],[Beta],[A],[B])	Inverse of the cumulative beta probability density function for the parameters (2)