TTEST

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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.

If type equals This test is performed
1 Paired
2 Two-sample equal variance (homoscedastic)
3 Two-sample unequal variance (heteroscedastic)

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.

ShowHow to copy an example

  1. Create a blank workbook or worksheet.
  2. Select the example in the Help topic.

 Note   Do not select the row or column headers.

Selecting an example from Help

Selecting an example from Help
  1. Press CTRL+C.
  2. In the worksheet, select cell A1, and press CTRL+V.
  3. To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
 
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Data 1 Data 2
3 6
4 19
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9 14
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2 5
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5 1
Formula Description (Result)
=TTEST(A2:A10,B2:B10,2,1) Probability associated with a Student's paired t-Test, with a two-tailed distribution (0.196016)
 
 
Applies to:
Excel 2003