5.5 Describing Variability: Range and Quartiles - Video

Key Ideas

  • One of the easiest ways to describe the variability of data is with the range. The range is defined to be the difference between the highest and lowest observations. When calculating the range, the outcome should never be negative. The only way for the range to be zero is if all observations represent the same numerical value.
  • The quartiles Q1 (the point below which 25% of the observations lie) and Q3 (the point below which 75% of the observations lie) give a better indication of the true variability of the data. More specifically, Q1 is the median of the data to the left of M (the median of the dataset). Q3 is the median of the data to the right of M.