# WorksheetFunction.T_Test Method (Excel)

Returns the probability associated with a Student 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

expression. `T_Test`( `_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, T_TEST uses the one-tailed distribution. If tails = 2, T_TEST 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), T_TEST returns the #N/A error value.

• The tails and type arguments are truncated to integers.

• If tails or type is non-numeric, 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.