\text{Step 1: Order the data set (already ordered):} \{1, 2, 2, 2, 3, 3, 3, 4, 4, 5, 6\}
\text{Step 2: Find } Q1 \text{ (the first quartile)}
Q1 = \text{median of the first half}
\{1, 2, 2, 2, 3\}
Q1 = 2
\text{Step 3: Find } Q3 \text{ (the third quartile)}
Q3 = \text{median of the second half}
\{3, 4, 4, 5, 6\}
Q3 = 4
\text{Step 4: Calculate the interquartile range (IQR)}
\text{Interquartile Range} = Q3 - Q1 = 4 - 2 = 2
[Solution: 2]