Both the ‘Range’ and ‘Interquartile Range’ measure the spread of our data set. That is they both tell us how spread out our data set is; so the bigger the value, the more spread out the data is and the smaller the value, the more condensed the data is.

But the Interquartile Range is a more realistic measure of spread than the Range. Let’s look at an example. Suppose we have the below data set. If we plot this set on a number line we get the following

Finding the ‘Range’
Finding the ‘Interquartile Range’ (IQR)

We can see a big difference between the two values but the IQR is the better measure of the spread.

Negative Numbers - Adding & Subtracting
Negative Numbers - Multiplying & Dividing