Measures of dispersion

• What are the two measures of dispersion?

  • Range
  • Standard deviation
• How to work out the range?

  Subtract the lowest number from the highest (sometimes adding 1)
• What is standard deviation?

  How much scores (on average) deviate from mean
• Evaluation of the Range:

  +Easy to calculate

  -Unrepresentative if there are extreme values
• Evaluation of Standard deviation:

  +More precise than the range

  -Distorted by extreme values