The Excel T.INV Function

Related Function:
T.INV.2T Function

Basic Description

The Excel T.INV function calculates the left-tailed inverse of the 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 function is new in Excel 2010, and so is not available in earlier versions of Excel.

The format of the function is:

T.INV( 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 left-tailed Student's T Distribution.
degrees_freedom-The number of degrees of freedom (must be ≥ 1).

T.Inv Function Example

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

The above chart on the right shows the left-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 function, as follows:

=T.INV( 0.25, 10 )

This gives the result -0.699812061.

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

T.Inv Function Errors

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

Common Errors

Occurs if either:

  • the supplied probability is ≤ 0 or > 1
  • the supplied degrees_freedom is < 1.
#VALUE!-Occurs if one or both of the supplied arguments are non-numeric.