# TTEST function

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

Important   This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. Although this function is still available for backward compatibility, you should consider using the new functions from now on, because this function may not be available in future versions of Excel.

For more information about the new function, see T.TEST function.

## Syntax

`TTEST(array1,array2,tails,type)`

The TTEST 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, TTEST uses the one-tailed distribution. If tails = 2, TTEST uses the two-tailed distribution.
• Type     Required. The kind of t-Test to perform.
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), TTEST returns the #N/A error value.
• The tails and type arguments are truncated to integers.
• If tails or type is nonnumeric, TTEST returns the #VALUE! error value.
• If tails is any value other than 1 or 2, TTEST returns the #NUM! error value.
• TTEST uses the data in array1 and array2 to compute a non-negative t-statistic. If tails=1, TTEST 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 TTEST 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 example may be easier to understand if you copy it to a blank worksheet.

1. Select the example in this article. If you are copying the example in Excel Online, copy and paste one cell at a time.
Important: Do not select the row or column headers.

Selecting an example from Help

1. Press CTRL+C.
2. Create a blank workbook or worksheet.
3. In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Online, repeat copying and pasting for each cell in the example.
Important: For the example to work properly, you must paste it into cell A1 of the worksheet.
4. To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

After you copy the example to a blank worksheet, you can adapt it to suit your needs.

A B
Data 1 Data 2
3 6
4 19
5 3
8 2
9 14
1 4
2 5
4 17
5 1
Formula Description (Result)
=TTEST(A2:A10,B2:B10,2,1) Probability associated with a Student's paired t-Test, with a two-tailed distribution (0.196016)

Applies to:
Excel 2010, Excel Web App, SharePoint Online for enterprises, SharePoint Online for professionals and small businesses