Learning Objectives

  • Explain what measures of dispersion tell us about a variable distribution compared with measures of center.
     
  • Identify a measure of dispersion appropriate for nominal or ordinal level data.
     
  • Describe the difference between the range and the interquartile range.
     
  • Discuss the relationship between the variance and the standard deviation.
     
  • Calculate and interpret the standard deviation with both grouped and ungrouped data.
     
  • Construct and interpret a boxplot and understand how it can reveal virtually everything about a variable distribution including the measure of center, variability, shape, and outliers.