Statistical testing: sign test

• Sign test:

  • convert data to nominal data
  • from table add up the pluses and minuses
  • take the less frequent sign and call this S
  • compare S value to critical value
• Sign test:

  The calculated value of S must be equal to or less than the critical value for there to be a significant difference.
• To use the sign test:

  • we need to be looking for a difference not an association
  • we need to have used a repeated measures design
  • we need data that is organised into categories (nominal data)
• Null hypothesis= no difference/association between two variables or in the population
• To use the table of critical values you need:

  • the significance level (0.05 or 5%)
  • number of participants in the investigation
  • whether the hypothesis is directional (one-tailed test) or non-directional (two-tailed test)