This tutorial explains how to perform one sample, two sample, and paired t tests in Excel.

Transcription

1 1 This tutorial explains how to perform one sample, two sample, and paired t tests in Excel. One Sample T test One sample t tests test whether the population mean underlying a sample set of numbers is different from a selected value. Excel does not have a one sample t test function. To work around this, replicate the number you are testing against (your selected value) as a second group. In the following example, we wish to test whether the Sample is different from the historical control of 8. Step 1: Click and highlight the empty cell where you would like results of the t test to be placed.

2 2 Step 2: Click the fx at the top of the spreadsheet. Once selected, the following screen will appear.

3 3 Step 3: Select the statistical category.

4 4 Step 4: Scroll down, select the TTEST (also seen as T.TEST) function and click OK. The following dialog box will appear.

5 5 Step 5: For Array 1, highlight first set of data. After you have highlighted, Excel will automatically fill in that argument.

6 6 Step 6: Repeat for Array 2, highlighting the second group of data.

7 7 Step 7: Tails specifies the number of distribution tails to return; type 2 for hypothesis of difference (two sided test). Use 3 as the t test type.

8 8 Step 8: Click OK. The result of this function is the p value for your t test. A p value below or equal to your significance level (typically 0.05) indicates a statistically significant difference; a p value greater than your significance level indicates no statistical difference. In this example, is less than the significance level of Therefore, we conclude that the sample is significantly different from the historical control of 8.

9 9 Two Sample T test Two sample t tests test whether the population means underlying two sample sets of numbers are different from each other. There are two forms of the two sample t tests. The first is the one sided test, which is appropriate when we wish to learn whether the mean of one group is greater than the mean of the other group. The second is the twosided test, which is appropriate when we wish to learn merely whether the means of the two groups are different. In the following example, we wish to utilize the two sided test to determine whether the mean for Group A is different from the mean for Group B. Step 1: Click and highlight the empty cell where you would like results of the t test to be placed.

10 10 Step 2: Click the fx at the top of the spreadsheet. Once selected, the following screen will appear.

11 11 Step 3: Select the statistical category.

12 12 Step 4: Scroll down, select the TTEST (also seen as T.TEST) function and click OK. The following dialog box will appear.

13 13 Step 5: For Array 1, highlight first set of data. After you have highlighted, Excel will automatically fill in that argument.

14 14 Step 6: Repeat for Array 2, highlighting the second group of data.

15 15 Step 7: Tails specifies the number of distribution tails to return; type 1 for the onesided test, type 2 for the two sided test. Use Type 2 as the t test type if assuming equal variance; use Type 3 if assuming unequal variance.

16 16 Step 8: Click OK. This function gives the p value for your t test. A p value below or equal to your significance level (typically 0.05) indicates a statistically significant difference; a p value greater than your significance level indicates no statistical difference. In this example, is greater than the significance level of Therefore, we conclude that there is not a statistical difference between Group A and Group B. Alternatively, we could state that there is insufficient evidence to determine whether there is a difference in Group A and Group B.

17 17 Paired T test Paired t tests test whether two set of related numbers are different from one another. There are two forms of the paired t tests. The first is the one sided test, which is appropriate when we wish to learn whether the mean of one group is greater than the mean of the other group. The second is the two sided test, which is appropriate when we wish to learn merely whether the means of the two groups are different. In the following example, we wish to utilize the two sided test to determine whether the mean for Pre is different from the mean for Post. Step 1: Click and highlight the empty cell where you would like results of the t test to be placed.

18 18 Step 2: Click the fx at the top of the spreadsheet. Once selected, the following screen will appear.

19 19 Step 3: Select the statistical category.

20 20 Step 4: Scroll down, select the TTEST (also seen as T.TEST) function and click OK. The following dialog box will appear.

21 21 Step 5: For Array 1, highlight first set of data. After you have highlighted, Excel will automatically fill in that argument.

22 22 Step 6: Repeat for Array 2, highlighting the second group of data.

23 23 Step 7: Tails specifies the number of distribution tails to return; type 1 for the onesided test, type 2 for the two sided test. Use 1 as the t test type.

24 24 Step 8: Click OK. This function gives the p value for your t test. A p value below or equal to your significance level (typically 0.05) indicates a statistically significant difference; a p value greater than your significance level indicates no statistical difference. In this example, is greater than the significance level of Therefore, we conclude that there is not a statistical difference between Pre and Post. Alternatively, we could state that there is insufficient evidence to determine whether there is a difference in Pre and Post.