Compatibility - TTEST Function

The TTEST function replaces the T.TEST function in Excel 2010.

Description

The 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.

TTEST (array1,array2,tails,type)

Argument	Description	Required/ Optional
Array1	The first data set.	Required
Array2	The second data set.	Required
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.	Required
Type	The kind of t-Test to perform. Look at the t-Test Table given below.	Required

Type	t-Test to Perform
1	Paired
2	Two-sample equal variance (homoscedastic)
3	Two-sample unequal variance (heteroscedastic)

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.
The tails and type arguments are truncated to integers.
If array1 and array2 have a different number of data points, and type = 1 (paired), TTEST returns the #N/A error value.
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.

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