# BETA.INV function

Returns the inverse of the beta cumulative probability density function (BETA.DIST).

If probability = BETA.DIST(x,...TRUE), then BETA.INV(probability,...) = x. The beta distribution can be used in project planning to model probable completion times given an expected completion time and variability.

## Syntax

BETA.INV(probability,alpha,beta,[A],[B])

The BETA.INV 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, BETA.INV returns the #VALUE! error value.

• If alpha ≤ 0 or beta ≤ 0, BETA.INV returns the #NUM! error value.

• If probability ≤ 0 or probability > 1, BETA.INV returns the #NUM! error value.

• If you omit values for A and B, BETA.INV uses the standard cumulative beta distribution, so that A = 0 and B = 1.

Given a value for probability, BETA.INV seeks that value x such that BETA.DIST(x, alpha, beta, TRUE, A, B) = probability. Thus, precision of BETA.INV depends on precision of BETA.DIST.

## 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 =BETA.INV(A2,A3,A4,A5,A6) Inverse of the cumulative beta probability density function for the parameters above. 2 