The IQR is essentially the range of the middle 50% of the data. Because it uses the middle 50%, the IQR is not affected by outliers or extreme values.

Does an outlier affect the range?

For instance, in a data set of {1,2,2,3,26} , 26 is an outlier. ... So if we have a set of {52,54,56,58,60} , we get r=60−52=8 , so the range is 8. Given what we now know, it is correct to say that an outlier will affect the ran g e the most.

What happens to the interquartile range when the outlier is removed?

The Interquartile Range is Not Affected By Outliers

Since the IQR is simply the range of the middle 50% of data values, it's not affected by extreme outliers.