The Excel T.INV.2T Function

Related Functions:
T.DIST.2T Function
T.INV Function

Basic Description

The Excel T.INV.2T 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 T.INV.2T function is new to Excel 2010. However, this function simply replaces the TINV function, that is available in earlier versions of Excel.

The format of the function is :

T.INV.2T( 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)


Excel uses an iterative method to calculate the T.Inv.2t function, and seeks to find a result, x, such that T.DIST.2T( x, degrees_freedom ) = probability.

Note that the Excel T.Inv.2t 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.

ie. The one-tailed inverse Student's T Distribution = T.INV.2T( 2*probability, degrees_freedom ).


T.Inv.2t Function Examples

Plot of Inverse of 2-Tailed Student's T Distribution with 10 Degrees of Freedom
2-Tailed Inverse Student's T-Distribution with 10 Degrees of Freedom

The chart on the right shows the two-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 T.Inv.2t function, as follows:

=T.INV.2T( 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 :

=T.INV.2T( 0.5, 10 )

which gives the result 0.699812061.


Further information and examples of the Excel T.Inv.2t function can be found on the Microsoft Office website.


T.Inv.2t Function Errors

If you get an error from your Excel T.Inv.2t function this is likely to be one of the following :

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