To find the interquartile range (IQR), ​first find the median (middle value) of the lower and upper half of the data. These values are quartile 1 (Q1) and quartile 3 (Q3). The IQR is the difference between Q3 and Q1.

Why do we find the interquartile range?

The interquartile range is the best measure of variability for skewed distributions or data sets with outliers. Because it's based on values that come from the middle half of the distribution, it's unlikely to be influenced by outliers.

How do you find quartiles and interquartile ranges?

The interquartile range is a value that is the difference between the upper quartile value and the lower quartile value. To find the interquartile range, simply take the upper quartile and subtract the lower quartile.