Key facts

• Use it for a difference, a related design and nominal data.
• Participants who show no change are left out.
• N is the number of participants left after removing the zeros.
• S is the number of times the less frequent sign occurs.
• The result is significant if S is equal to or less than the critical value.

How to do it

1. Write + or − for each participant (second score minus first).
2. Cross out the zeros and count what is left. That is N.
3. Count the pluses and minuses. The smaller number is S.
4. Find the critical value using N, one- or two-tailed, and the significance level.
5. For a one-tailed test, check the results go in the predicted direction.
6. Compare S with the critical value and write a conclusion that includes all the values.