- Interquartile Range (IQR) =
, with
as the upper quartile and
as the lower quartile.
Firstly, rearrange the data so that it's in ascending order:
Next, find the median:
Now to find the lower quartile, find the "median" of the data set that's to the left of 99:
Now to find the upper quartile, it's the similar process as finding the lower quartile, except that you are finding the "median" of the data set to the right of 99:
Now that we have the upper and lower quartile, subtract them:
<u>In short, the IQR of this data set is 13.5.</u>