Interquartile Range

Box-and-whisker plots are helpful in interpreting the distribution of data. From looking at a box and whisker plot, you can tell the median and range very quickly.

It is useful to see data displayed graphically.   One way to do this is use the box and whisker plot.  A box and whisker plot is a diagram that summarizes data using the median, the upper and lower quartiles, and the extreme values (minimum and maximum).  Box and whisker plots are also known as box plots.

They are constructed using a five-number summary of the data:

  1. Minimum (lowest number in the data)
  2. Q1 (lower quartile, the median of the bottom half of the data)
  3. Q2 (median of all the data)
  4. Q3 (upper quartile, the median of the top half of the data)
  5. Maximum (highest number in the data)

The interquartile range (IQR) is the difference between the first and third quartiles.