The sign test

• What is significance in the sign test?

  • The difference between two sets of data is greater than what would occur by chance.
  • To find out if the difference is significant we need to use a statistical test.
• What is the probability in the sign test?

  Probability (p) refers to the likelihood that certain events will occur.
• What is the accepted level of probability?


  • 0.05 (5%)
  • This is the level at which a researcher decides to accept or reject the null hypothesis.
• What is the calculated value?

  It’s compared with a critical value to decide whether the result is significant or not.
• How do you find the critical value?

  1. The significant value (usually 0.05).
  2. The number of participants (N value).
  3. Whether the hypotheses is directional (one-tailed test) or non-directional (two-tailed test).
• When is the sign test used?

  To analyse the difference in score between related items.
• How do you calculate in the sign test?

  1. The score for condition B is subtracted from condition A to produce the sign of difference (+ or -).
  2. Add up the number of + and -.
  3. Participants who achieved the same score in both conditions should Be disregarded.
  4. The S value (calculated value) is the total of the less frequent sign.
• How do you write an answer for the sign test?

  • Is it significant or not significant?
  • At what level? E.g. at 0.05% level.
  • What is the value of N? E.g. when N=20.
  • A one-tailed or two-tailed test?
  • Is the calculated value of S greater or smaller than the critical value?