# WorksheetFunction.TTest Method (Excel)

Office 2013 and later
 Contribute to this content Use GitHub to suggest and submit changes. See our guidelines for contributing to VBA documentation.

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. 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.

## Syntax

expression .TTest(Arg1, Arg2, Arg3, Arg4)

expression A variable that represents a WorksheetFunction object.

### Parameters

Name

Required/Optional

Data Type

Description

Arg1

Required

Variant

Array1 - the first data set.

Arg2

Required

Variant

Array2 - the second data set.

Arg3

Required

Double

Tails - specifies the number of distribution tails. If tails = 1, TTEST uses the one-tailed distribution. If tails = 2, TTEST uses the two-tailed distribution.

Arg4

Required

Double

Type - the kind of t-Test to perform.

Double

## Remarks

If type equals

This test is performed

1

Paired

2

Two-sample equal variance (homoscedastic)

3

Two-sample unequal variance (heteroscedastic)

• 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.