T.INV.2T function
Returns the twotailed inverse of the Student's tdistribution.
Syntax
T.INV.2T(probability,deg_freedom)
The T.INV.2T function syntax has the following arguments:

Probability Required. The probability associated with the Student's tdistribution.

Deg_freedom Required. The number of degrees of freedom with which to characterize the distribution.
Remarks

If either argument is nonnumeric, T.INV.2T returns the #VALUE! error value.

If probability <= 0 or if probability > 1, T.INV.2T returns the #NUM! error value.

If deg_freedom is not an integer, it is truncated.

If deg_freedom < 1, T.INV.2T returns the #NUM! error value.

T.INV.2T returns that value t, such that P(X > t) = probability where X is a random variable that follows the tdistribution and P(X > t) = P(X < t or X > t).

A onetailed tvalue can be returned by replacing probability with 2*probability. For a probability of 0.05 and degrees of freedom of 10, the twotailed value is calculated with T.INV.2T(0.05,10), which returns 2.28139. The onetailed value for the same probability and degrees of freedom can be calculated with T.INV.2T(2*0.05,10), which returns 1.812462.
Given a value for probability, T.INV.2T seeks that value x such that T.DIST.2T(x, deg_freedom, 2) = probability. Thus, precision of T.INV.2T depends on precision of T.DIST.2T.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?

Select the example in this article.
Important Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In Excel, create a blank workbook or worksheet.

In the worksheet, select cell A1, and press CTRL+V.
Important For the example to work properly, you must paste it into cell A1 of the worksheet.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.

