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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.

Syntax

TTEST(array1,array2,tails,type)

Array1   is the first data set.

Array2   is the second data set.

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.

Type   is the kind of t-Test to perform.

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.