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.
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.
- 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.
- If x < 0, then TDIST returns the #NUM! error value.
- If tails = 1, TDIST is calculated as TDIST = P( X>x ), where X is a random variable that follows the t-distribution. If tails = 2, TDIST is calculated as TDIST = P(|X| > x) = P(X > x or X < -x).
- Since x < 0 is not allowed, to use TDIST when x < 0, note that TDIST(-x,df,1) = 1 – TDIST(x,df,1) = P(X > -x) and TDIST(-x,df,2) = TDIST(x df,2) = P(|X| > x).
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
- Create a blank workbook or worksheet.
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Selecting an example from Help
- Press CTRL+C.
- In the worksheet, select cell A1, and press CTRL+V.
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||Value at which to evaluate the distribution
||Degrees of freedom
||Two-tailed distribution (0.054644927, or 5.46 percent)
||One-tailed distribution (0.027322464 or 2.73 percent)
Note To view the number as a percent, select the cell and, on the Format menu, click Cells. Click the Number tab, and then click Percentage in the Category box.