If 25% of items are less than 20 and 25% are more than 40, the quartile deviation is:

Correct option is D

Given:
25% of items are less than 20
25% of items are more than 40
Formula used:
Quartile deviation = $$\frac{Q_3 - Q_1}{2}$$​​
Solution:
Since 25% of items are less than 20,
​$$Q_1 = 20$$​​
Since 25% of items are more than 40,
​$$Q_3 = 40$$​​
Quartile deviation
​$$= \frac{40 - 20}{2}= \frac{20}{2}= 10$$​​
The correct answer is (d) 10.