Improved box plot

One problem with basic box plots is that they cannot distinguish between a data set with an outlier and one with a skew distribution. A modification displays some extreme values as separate crosses and allows this distinction to be made.

Which extreme values are displayed as crosses?

The interquartile range (IQR) is the distance between the upper and lower quartiles (i.e. the length of the central box in the box plot). Any values more than 1.5 times this distance from the box are displayed with separate crosses.