The Excel TTEST Function

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Related Function:

TDIST Function

TTEST and T.TEST

In Excel 2010, the TTEST function has been renamed T.TEST.

Although the Ttest function has been replaced, Excel 2010 has kept this function, (stored within the list of compatibility functions), for compatibility with earlier versions of Excel.

Basic Description

The Excel TTEST function calculates the probability associated with the Student's T Test, which is commonly used for identifying whether two data sets are likely to have come from the same two underlying populations with the same mean.

The format of the function is :

TTEST( array1, array2, tails, type )

where the function arguments are:

array1

The first data set

array2

The second data set (must have the same length as array1)

tails

The number of tails for the distribution. This must be either :

1	-	uses the one-tailed distribution
2	-	uses the two-tailed distribution

type

An integer that represents the type of t-test. This can be either :

1	-	Paired T-Test
2	-	Two-sample equal variance T-Test
3	-	Two-sample unequal variance T-Test

Examples

	A	B
1	4	8
2	5	3
3	2	7
4	5	3
5	8	5
6	9	2
7	3	2
8	2	7
9	3	9
10	8	4
11	9	4
12	5	7

Columns A and B of the spreadsheet on the right contain two arrays of data.

The probability associated with the Student's paired t-test with a one-tailed distribution, for the two arrays of data can be calculated using the Excel Ttest function as follows :

=TTEST( A1:A12, B1:B12, 1, 1 )

This gives the result 0.449070689.

The probability associated with the Student's paired t-test with a two-tailed distribution, for the same two arrays of data is calculated by :

=TTEST( A1:A12, B1:B12, 2, 1 )

This gives the result 0.898141379, which is double the probability associated with the one-tailed test.

Further information and examples of the Excel Ttest function can be found on the Microsoft Office website.