How to Use Excel's TTEST Function

By eHow Computers Editor

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Excel's TTEST function calculates the probability that two samples are from the same population, assuming the populations have the same mean. TTEST returns the probability of a Student's t-Test, a method of testing a hypothesis made about the mean of a sample population. It is named after William Sealy Gosset who published the first paper on the subject in 1908 under the pseudonym "Student." Here's how to use Excel's TTEST function.

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Instructions

Difficulty: Moderately Challenging

Step1

Learn the syntax for TTEST. It is TTEST (array_1, array_2, tails, type).

Step2

Provide array_1 and array_2 as the data sets. TTEST will use this data to compute a nonnegative t-statistic. TTEST will return #N/A if these data sets have different sizes and the type is 1 (paired t-Test.)

Step3

Use tails to indicate the desired number of distribution tails. TTEST will return #NUM! if tails is a number other than 1 or 2. TTEST will return #VALUE! if tails is nonnumeric.

Step4

Input a value of 1 for tails to use a one tailed distribution. TTEST will return the probability of a higher t-statistic, assuming that the populations represented by array_1 and array_2 have the same mean. A value of 2 will use a two-tailed distribution that returns a value twice as high as the one returned for a one-tailed distribution. This value is the probability that the absolute value of the t-statistic is higher using the "same population means" assumption.

Step5

Specify type as the type of t-Test to perform. A type of 1 indicates a paired t-Test, a type of 2 is a two-sample equal (homoscedastic) variance and a type of 3 indicates a two-sample unequal (heteroscedastic) variance. TTEST will return #VALUE! if type is nonnumeric.