# 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. |

### Return value

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.