The Excel LOGNORM.INV function calculates the inverse of the Cumulative Log-Normal Distribution Function of x, for a supplied probability. The Lognorm.Inv function is new in Excel 2010 and so is not available in earlier versions of Excel. However, the function is simply a new version of the Loginv function that is available in earlier versions of Excel.
Syntax: LOGNORM.INV( probability, mean, standard_dev )
Where the function arguments are:
|probability||–||The value at which you want to evaluate the inverse function|
|mean||–||The arithmetic mean of ln(x)|
|standard_dev||–||The standard deviation of ln(x)|
Lognorm.Inv Function Example
mean ln(x) = 2 & standard deviation ln(x) = 0.2
The chart on the right shows the the Inverse Log-Normal Cumulative Distribution Function for a variable x. The mean of ln(x) = 2 and the standard deviation of ln(x) = 0.2.
If you want to calculate the value of x for a probability of 0.3, this can be done using the Excel Lognorm.Inv function, as follows:
=LOGNORM.INV( 0.3, 2, 0.2 )
This gives the result 6.653346076.
Lognorm.Inv Function Errors
If you get an error from your Excel Lognorm.Inv function this is likely to be one of the following:
|#NUM!||–||Occurs if either the supplied probability argument is ≤ 0 or ≥ 1 or the supplied standard_dev argument is ≤ 0|
|#VALUE!||–||Occurs if any of the the supplied arguments are non-numeric.|