Interquartile Range

Quartile

Quartiles are values that divide a dataset into quarters. Each divider is labeled as Q1, Q2, Q3.

Q1 represents the median of the lower half of the data
Q2 represents the median
Q3 represents the median of the upper half of the data

Interquartile Range (IQR)

Definition

Box and Whisker Plot

Example

                    
                             +−−−−−+−+     
               * |−−−−−−−−−−−|     | |−−−−−−−−−−−|
                             +−−−−−+−+    
                    
 +−−−+−−−+−−−+−−−+−−−+−−−+−−−+−−−+−−−+−−−+−−−+−−−+   number line
 0   1   2   3   4   5   6   7   8   9   10  11  12

the leftmost point represents the smallest datum point, the beginning of the box represents Q1, the middle line represents Q2, the end of the box represents Q3, and the rightmost point represents the largest datum.