TDIST Function Returns #NUM! If X Argument Is Negative (173923)


The information in this article applies to:

  • Microsoft Excel 97 for Windows
  • Microsoft Excel for Windows 95
  • Microsoft Excel for Windows 5.0
  • Microsoft Excel 98 Macintosh Edition
  • Microsoft Excel for Windows 95 7.0a
  • Microsoft Excel for Windows 4.0
  • Microsoft Excel for Windows 4.0a
  • Microsoft Excel for Windows 5.0c
  • Microsoft Excel for Windows NT 5.0
  • Microsoft Excel for the Macintosh 4.0
  • Microsoft Excel for the Macintosh 5.0
  • Microsoft Excel for the Macintosh 5.0a
This article was previously published under Q173923

SYMPTOMS

In Microsoft Excel, if you enter a formula that uses the TDIST function, the formula may return a #NUM! error. This behavior may occur even when you use a value greater than or equal to 1 for the Degrees_Freedom argument and a value of 1 or 2 for the Tails argument.

CAUSE

This behavior occurs if the X argument is negative (less than zero) in the following syntax 
   TDIST(x,degrees_freedom,tails)
where X is the numeric value at which to evaluate the distribution. For example, the following formula 
   =TDIST(-1.96,60,2)
returns a #NUM! error because the X argument is negative.

This behavior is by design of Microsoft Excel.

RESOLUTION

To resolve this problem, use a value that is greater than or equal to zero for the X argument in the TDIST function.

MORE INFORMATION

In Microsoft Excel, the TDIST function allows you to calculate the Student's t-distribution. The t-distribution is used in the hypothesis testing of small sample data sets. You can use the TDIST function in place of a table of critical values for the t-distribution.

The "Function Reference" for Microsoft Excel 4.x and the Microsoft Excel Help file for other versions of Microsoft Excel include the following information about the TDIST function:

  • If any argument is nonnumeric, the TDIST function returns a #VALUE! error.
  • The Degrees_Freedom and Tails arguments are truncated to integers.
  • If Degrees_Freedom is less than 1, the TDIST function returns a #NUM! error.
  • If Tails has a value other than 1 or 2, the TDIST function returns a #NUM! error.
The "Function Reference" and Help files do not mention any restrictions for the X argument. However, the following additional information applies:

If X is less than 0, the TDIST function returns a #NUM! error.

Modification Type:MinorLast Reviewed:8/17/2005
Keywords:kbprb KB173923
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