The Excel NORM.INV Function

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Related Functions:  NORM.DIST NORM.S.INV

Normal Distribution

The Normal distribution is a continuous probability function that is given by the formula :

where μ is the mean of the distribution, σ² is the variance, and x is the independent variable for which you want to evaluate the function.

The Cumulative Normal Distribution function is given by the integral, from - infinity to x, of the Normal Probability Density function.

More information on the Normal Distribution is given on the Wikipedia Normal Distribution Page

Basic Description

The Excel NORM.INV function calculates the inverse of the Cumulative Normal Distribution Function for a supplied value of x, and a supplied distribution mean & standard deviation.

The Norm.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 Norminv function that is available in earlier versions of Excel.

The format of the function is :

Where the function arguments are:

Excel uses an interative method to calculate the Norm.Inv function and seeks to find a result, x, such that:

Inverse Normal Cumulative Distribution with mean = 5 & std. dev. = 2

Norm.Inv Function Example

The chart on the right shows the the Inverse Normal Cumulative Distribution Function with a Mean of 5 and a Standard Deviation of 2.

If you want to calculate the value of this function when probability = 0.6, this can be done using the Excel Norm.Inv function, as follows:

This gives the result 5.506694206.

Further information and examples of the Excel Norm.Inv function can be found on the Microsoft Office website.

Trouble Shooting

If you get an error from your Excel Norm.Inv function this is likely to be one of the following: