Learn how to calculate the interquartile range from a variety of different data types and draw and interpret box-and-whisker diagrams.

The interquartile range shows the range in values of the central 50% of the data. To find the interquartile range, subtract the value of the lower quartile Q1 from the value of the upper quartile ...

We discourage the use of a diagnostic for normality: the interquartile range divided by the standard deviation. This statistic has been suggested in several introductory statistics books as a method ...

Others members of the family include the inter-quartile range, the mode and the range. Those three I explain here and in a later column I will turn to standard deviations.