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.
Are quartiles sensitive to outliers?
Resistance to Outliers
The primary advantage of using the interquartile range rather than the range for the measurement of the spread of a data set is that the interquartile range is not sensitive to outliers.
Are Q1 and Q3 affected by outliers?
We can use the IQR method of identifying outliers to set up a “fence” outside of Q1 and Q3. Any values that fall outside of this fence are considered outliers. ... Any observations that are more than 1.5 IQR below Q1 or more than 1.5 IQR above Q3 are considered outliers.
