Learning Objectives

  • Explain the difference between measures of dispersion and measures of central tendency.
  • Explain why measures of dispersion must be reported in addition to measures of central tendency.
  • Define kurtosis, leptokurtosis, and platykurtosis.
  • Explain and know the relevant formulas for variation ratio, range, variance, and standard deviation.
  • Apply the correct measure(s) of dispersion to any given variable based on that variable’s level of measurement.
  • Explain the normal curve and the concept behind two-thirds of cases being within one standard deviation of the mean.
  • Calculate the upper and lower boundaries of the typical range of scores in a normal distribution based on the mean and the standard deviation.