Range and Quartiles

Find the range of: $3$, $8$, $5$, $12$, $7$.

• 1Highest value: $12$. Lowest value: $3$
• 2Subtract: $12-3$

Answer: $9$

Find Q1, Q3, and the IQR of: $2$, $3$, $5$, $7$, $8$, $9$, $10$, $12$, $15$.

• 1There are $9$ values. The overall median (5th value) is $8$
• 2Lower half (values below the median): $2$, $3$, $5$, $7$. Q1 is the median of these: ($3+5$) ÷ $2=4$
• 3Upper half (values above the median): $9$, $10$, $12$, $15$. Q3 is the median of these: ($10+12$) ÷ $2=11$
• 4IQR = Q3 − Q$1=11-4=7$

Answer: Q$1=4$, Q$3=11$, IQR = $7$