T Test - Paired

To test hypotheses comparing means of two non-independent populations.

Example: Consider a sample of measurements of the company A lab and a sample of measurements of the company B lab (the values are in the following table). Tests of two laboratories are in the same pattern, so there is a correlation between them, that is, the samples are dependent. Evaluate the measurements compatibility between the company A lab and the company B level.o

^{click here to download the data}

To use the tool T Test - Paired, the user must follow these steps:

1. Access the menu:

Action Basic Statistics Means T Test -  Paired.

2. The following window will appear;

3. With the cursor in the field Data Set 1, select the column (table or row) that contains the data referring to sample 1. The data must be numeric;

4. With che cursor in the field Data Set 2, select the column (table or row) that contains the data referring to sample 2. The data must be numeric;

5. In the field Confidence Level we type the confidence level, in this case we type 0.95 (95%);

6. In the field Alternative Hypothesis, select among the options Not equal, Lower than or Greater than. In this example we want to test it there is or not significant difference between the two samples, we select Not equal;

7. In Show Results, we select between the options Current Cell or New Sheet. We suggest the option New Sheet because Action does not have the undo command;

REMARK: When choosing the option Current Cell the results will be printed from the cell where the cursor is. In this case, the user must put the cursor in an appropriate position previously (before step 1)

8. To finish, click Ok.

Results and  Interpretation

Once the process is finished, the following results will be shown.

The statistics of the test is -0.315. As the p-value is 75.62%, bigger than 5%, we do not reject the null hypothesis of compatibility of measurements between the laboratories, at a 95% confidence level.