# T.TEST function

Returns the probability associated with a Student's t-Test. Use T.TEST to determine whether two samples are likely to have come from the same two underlying populations that have the same mean.

## Syntax

`T.TEST(array1,array2,tails,type)`

The T.TEST function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):

• Array1     Required. The first data set.
• Array2     Required. The second data set.
• Tails     Required. Specifies the number of distribution tails. If tails = 1, T.TEST uses the one-tailed distribution. If tails = 2, T.TEST uses the two-tailed distribution.
• Type     Required. The kind of t-Test to perform.

## Parameters

If type equals This test is performed
1 Paired
2 Two-sample equal variance (homoscedastic)
3 Two-sample unequal variance (heteroscedastic)

## Remarks

• If array1 and array2 have a different number of data points, and type = 1 (paired), T.TEST returns the #N/A error value.
• The tails and type arguments are truncated to integers.
• If tails or type is nonnumeric, T.TEST returns the #VALUE! error value.
• If tails is any value other than 1 or 2, T.TEST returns the #NUM! error value.
• T.TEST uses the data in array1 and array2 to compute a non-negative t-statistic. If tails=1, T.TEST returns the probability of a higher value of the t-statistic under the assumption that array1 and array2 are samples from populations with the same mean. The value returned by T.TEST when tails=2 is double that returned when tails=1 and corresponds to the probability of a higher absolute value of the t-statistic under the “same population means” assumption.

## Example

The workbook below shows examples of this function. Inspect them, change existing formulas, or enter your own formulas to learn how the function works.

To work more in-depth with the example data in Excel, download the embedded workbook to your computer, and then open it in Excel.

Applies to:
Excel 2013, Excel Online