In Excel 2010, the Betainv function has been replaced by the Beta.Inv function, which has improved accuracy.
The Excel BETAINV function uses an iterative procedure to calculate the inverse of the cumulative beta probability density function for a supplied probability.
The syntax of the function is:
Where the function arguments are listed in the table below:
|probability||-||The probability of the Beta distribution, for which you want to find the value of x.|
|alpha||-||A parameter of the distribution (must be > 0).|
|beta||-||A parameter of the distribution (must be > 0).|
|[A]||-||[A] takes the default value 0).(If omitted,|
|[B]||-||[B] takes the default value 1).(If omitted,|
Note that, if the arguments [A] and [B] are set to 0 and 1 respectively, the calculation becomes the Inverse Standard Cumulative Beta Distribution.
The charts below show the Cumulative Beta Distribution and the Inverse Cumulative Beta Distribution, with the parameter alpha set to 4 and the parameter beta set to 5.
Standard Cumulative Beta Distribution Function with α = 4 and β = 5
Inverse Standard Cumulative Beta Distribution with α = 4 and β = 5
Note that, in the above example, the arguments [A] and [B] have been supplied to the functions as the values 0 and 1. However, these values could have been omitted from the function, as their values, if omitted, default to 0 and 1.
Further details and examples of the Excel Betainv function are provided on the Microsoft Office website.
If you get an error from the Excel Betainv function this is likely to be one of the following:
|#VALUE!||-||Occurs if any of the supplied arguments are non-numeric.|