# The Excel TINV Function

TINV & T.INV.2T

In Excel 2010, the TINV function has been replaced by the T.INV.2T function.

Although the Tinv function has been replaced, it is still available in Excel 2010, (stored within the list of compatibility functions), to allow compatibility with earlier versions of Excel.

However, the Tinv function may not be available in future versions of Excel, so it is advised that you use the T.INV.2T function if possible.

Related Function:
TDIST Function

## Function Description

The Excel TINV function calculates the inverse of the two-tailed Student's T Distribution, which is a continuous probability distribution that is frequently used for testing hypotheses on small sample data sets.

The syntax of the function is:

TINV( probability, degrees_freedom )

Where the function arguments are:

 probability - The probability (between 0 and 1) for which you want to evaluate the inverse of the two-tailed Student's T Distribution. degrees_freedom - The number of degrees of freedom (must be ≥ 1).

Note that:

• Excel uses an iterative method to calculate the result of the Tinv function and seeks to find a result, x, such that TDIST( x, degrees_freedom, 2 ) = probability.
• The Excel Tinv Function calculates the inverse of the two-tailed Student's T Distribution. If you want to calculate the inverse of the one-tailed t-distribution you can simply double the probability.

I.e. The one-tailed inverse Student's T Distribution = TINV( 2*probability, degrees_freedom ).

## Tinv Function Examples 2-Tailed Inverse Student's T-Distribution with 10 Degrees of Freedom

The above chart on the right shows the 2-tailed Inverse Student's T Distribution with 10 degrees of freedom.

If you want to calculate the value of this function for a probability of 0.25, this can be done using the Excel Tinv function, as follows:

=TINV( 0.25, 10 )

This gives the result 1.221255395.

If you want to calculate the value of the one-tailed inverse Student's T-Distribution for a probability of 0.25, this can be done by doubling the probability, as follows:

=TINV( 0.5, 10 )

This gives the result 0.699812061.

For further information and examples of the Excel Tinv function, see the Microsoft Office website.

## Tinv Function Errors

If you get an error from the Excel Tinv function this is likely to be one of the following:

Common Errors
 #NUM! - Occurs if either:The supplied probability is ≤ 0 or > 1orThe supplied degrees_freedom is < 1. #VALUE! - Occurs if one or both of the supplied arguments are non-numeric.