Excel - GAMMAINV Function

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GAMMAINV Function

The Excel GAMMAINV function retrieves the gamma cumulative distributions inverse. This function is employed in various fields, including medical, logistics, risk, and quality control management. For instance, it is used to determine the recovery time of hypertension patients from heart-related diseases.

The mathematical notation is t = GAMMADIST(x, ...) then GAMMAINV(t, ...) = x

The GAMMAINV function interchanges the GAMMA.INV function appended in Excel 2010.

Note − This function has been interchanged with new powerful functions with excellent accuracy. However, this function is still exclusive to backward compatibility.

Syntax

The syntax of GAMMAINV function is as follows −

GAMMAINV (probability,alpha,beta)

Compatibility

This advanced Excel function is compatible with the following versions of MS-Excel −

• Excel for Microsoft 365
• Excel for Microsoft 365 for Mac
• Excel for the Web
• Excel 2021
• Excel 2021 for Mac
• Excel 2019
• Excel 2019 for Mac
• Excel 2016

Arguments

You can use the following arguments with the GAMMAINV function −

Points to Remember

• The GAMMAINV function retrieves the #VALUE! error if any of its arguments contains the text string.
• Either the probability is negative or greater than 1, GAMMAINV will receive the #NUM! Error.
• Either the Alpha or Beta value is less than or equal to zero, GAMMAINV returns the #NUM! Error.
• This function employs the iterative search technique. Suppose the search is unsuccessful after 100 iterations; the GAMMAINV function will retrieve the #N/A error.
• GAMMAINV function will retrieve the standard gamma distribution if the value of the Beta is equal to 1.

Examples of GAMMAINV Function

Practice the following examples to learn the use of the GAMMAINV function in Excel.

Example 1

Suppose the sales manager wishes to compute the time to failure of the electronic item Air fryer through the GAMMAINV function.

Solution

Assume the sample dataset, where the distinct probability values are defined in the range C3:C5. Calculate the GAMMAINV function for each given probability to evaluate the time to failure. Enter the formula =GAMMAINV(C3,C7,C8) in the E3 cell and press the Enter tab to get the result.

Similarly, enter the formula =GAMMAINV(C4,C7,C8) in the E4 cell and press the Enter tab.

Therefore, the resultant value is 45.133 at the specified probability of 0.92, representing the time to failure.

Now, calculate the GAMMAINV function at the specified probability of 0.55, and enter the formula =GAMMAINV(C5,C7, C8) in the E5 cell.

And then press the Enter tab to get the resulting value.

Example 2

The GAMMAINV function retrieves the #VALUE! error if any of its arguments contains the text string.

Solution

Example 3

Either the probability is negative or greater than 1, the GAMMAINV function will receive the #NUM! Error.

Solution

Write the formula =GAMMAINV(23,9,12) in the B3 cell. Here, the probability value is 23, greater than 1.

Therefore, the #NUM! error will occur.

Example 4

Either the Alpha or Beta value is less than and equal to zero, GAMMAINV returns the #NUM! Error.

Solution

If the value of Alpha is negative −

Enter the formula =GAMMAINV(0.34,-4,12) in the B3 cell and press the Enter tab. The #NUM! will then be obtained after executing this function.

If the value of Beta is 0 −

As you can notice in the screenshot, the third argument, Beta is 0. Enter the formula =GAMMAINV(0.34,4,0) in the B3 cell.

Once you press the Enter tab, the #NUM! error will be obtained.

Example 5

GAMMAINV function will retrieve the standard gamma distribution if the value of the Beta is equal to 1.

Solution

To accomplish this, you need to use GAMMA.DIST function. Here, you may enter the Beta value in the C8 cell. Now, write the formula =GAMMA.DIST(E5,C7,C8,TRUE) in the E9 cell and press the Enter tab.

The resulting value is 0.55, the same as that of probability 3, which is 0.55, specified in the C5 cell.