TDIST

See Also

Returns the Percentage Points (probability) for the Student t-distribution where a numeric value (x) is a calculated value of t for which the Percentage Points are to be computed. The t-distribution is used in the hypothesis testing of small sample data sets. Use this function in place of a table of critical values for the t-distribution.

Syntax

TDIST(x,degrees_freedom,tails)

X is the numeric value at which to evaluate the distribution.

Degrees_freedom is an integer indicating the number of degrees of freedom.

Tails specifies the number of distribution tails to return. If tails = 1, TDIST returns the one-tailed distribution. If tails = 2, TDIST returns the two-tailed distribution.

Remarks

If any argument is nonnumeric, TDIST returns the #VALUE! error value.
If degrees_freedom < 1, TDIST returns the #NUM! error value.
The degrees_freedom and tails arguments are truncated to integers.
If tails is any value other than 1 or 2, TDIST returns the #NUM! error value.
TDIST is calculated as TDIST = p( x<abs(X)), where X is a random variable that follows the t-distribution.

Example

The example may be easier to understand if you copy it to a blank spreadsheet.

How?

Create a blank spreadsheet.
Select the example in the Help topic.

Selecting an example from Help
Press CTRL+C.
In the spreadsheet, select cell A1, and press CTRL+V.
To switch between viewing the formula that returns the result and the result in the cell, select the cell and press F2 and then ENTER, or click Commands and Options on the spreadsheet toolbar, click the Formula tab, and look in the Formula in active cell (active cell) box.

Data	Description
1.96	Value at which to evaluate the distribution
60	Degrees of freedom
Formula	Description (Result)
=TDIST(A2,A3,2)	Two-tailed distribution (0.054644927 or 5.46 percent)
=TDIST(A2,A3,1)	One-tailed distribution (0.027322463 or 2.73 percent)

Note To view the number as a percent, select the cell and click Commands and Options on the toolbar. Click the Format tab, and then click Percent in the Number Format box.