The Range and Interquartile Range (IQR) are ways to understand how spread out numbers are in statistics.

Range

• What it is: The range shows the difference between the biggest and smallest numbers in a set of data.
• How to calculate it: $\text{Range} = \text{Biggest number} - \text{Smallest number}$
• Example: If we have these numbers: {4, 8, 15, 16}, the range is $16 - 4 = 12$.

Interquartile Range (IQR)

• What it is: The IQR tells us about the range of the middle 50% of the numbers. It is found by looking at the first quartile (Q1) and the third quartile (Q3).
• How to calculate it: $\text{IQR} = Q3 - Q1$
• Example: For the numbers {1, 3, 5, 7, 9}, Q1 = 3 and Q3 = 7. So the IQR is $7 - 3 = 4$.

In short, the Range shows how wide the numbers are spread apart, while the IQR focuses on the middle part of the data.