BETAINV function

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

Important: This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. Although this function is still available for backward compatibility, you should consider using the new functions from now on, because this function may not be available in future versions of Excel.

For more information about the new function, see BETA.INV function.

Syntax

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

The BETAINV function syntax has the following arguments:

• Probability     Required. A probability associated with the beta distribution.

• Alpha     Required. A parameter of the distribution.

• Beta     Required. A parameter the distribution.

• A     Optional. A lower bound to the interval of x.

• B     Optional. An 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.

Given a value for probability, BETAINV seeks that value x such that BETADIST(x, alpha, beta, A, B) = probability. Thus, precision of BETAINV depends on precision of BETADIST.

Example

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

Data	Description
0.685470581	Probability associated with the beta distribution
8	Parameter of the distribution
10	Parameter of the distribution
1	Lower bound
3	Upper bound
Formula	Description	Result
=BETAINV(A2,A3,A4,A5,A6)	Inverse of the cumulative beta probability density function for the parameters above	2