Find range of 12, 9, 15, 20, 13.

Answer: \(20-9=11\).

If \(Q_1=18\), \(Q_3=31\), find IQR.

Answer: 13.

Dataset A and B have same mean. A has SD 2, B has SD 8. Which is more consistent?

Answer: A (smaller SD).

Why is IQR preferred over range when outliers exist?

Answer: IQR focuses on middle 50% and is less distorted by extreme values.

Checkpoints