The Excel T.DIST.2T Function

Function Description

The Excel T.DIST.2T function calculates 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.DIST.2T function is new to Excel 2010. However, this function (along with the new T.DIST.RT function) replaces the TDIST function, which is available in earlier versions of Excel.

The syntax of the T.DIST.2T function is:

T.DIST.2T( x, degrees_freedom )

where the function arguments are:

x-The value at which you want to evaluate the two-tailed Student's T-Distribution.
degrees_freedom-The number of degrees of freedom (must be ≥ 1).

Note that the Excel T.Dist.2t Function doesn't allow the argument x to be < 0. Therefore, if you want to calculate the two-tailed Student's T Distribution for values of x that are less than 0, you should use the relationship:

T.DIST.2T( -x, df ) = T.DIST.2T( x, df )

T.Dist.2t Function Example

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

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

If you want to calculate the value of this function at x = 1, this can be done using the Excel T.Dist.2t function, as follows:

=T.DIST.2T( 1, 10 )

This gives the result 0.340893132, or 34.09%.


If you want to calculate the value of the function, at x = -1, this must be done using the relationship T.DIST.2T( -x, df ) = T.DIST.2T( x, df ).

Therefore, the formula to calculate the function at x = -1 is simply:

=T.DIST.2T( 1, 10 )

which again, gives the result 0.340893132, or 34.09%.


For further details and examples of the Excel T.Dist.2t function, see the Microsoft Office website.


T.Dist.2t Function Errors

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

Common Errors
#NUM!-

Occurs if either:

  • The supplied value of x is < 0
or
  • The supplied value of degrees_freedom is < 1.
#VALUE!-Occurs if one or both of the supplied arguments are non-numeric.