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# WorksheetFunction.TDist Method (Excel)

Office 2013

Published: July 16, 2012

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.

Important

This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. This function is still available for compatibility with earlier versions of Excel. However, if backward compatibility is not required, you should consider using the new functions from now on, because they more accurately describe their functionality.

expression .TDist(Arg1, Arg2, Arg3)

expression A variable that represents a WorksheetFunction object.

### Parameters

Name

Required/Optional

Data Type

Description

Arg1

Required

Double

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

Arg2

Required

Double

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

Arg3

Required

Double

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.

### Return Value

Double

• 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).