Question

Which of the following gives the inter quartile range of the data?

• A. 50
• B. 45
• C. 55
• D. 20

Answer 1

The correct option is D 20

The given dot plot is


The data set is

40, 50, 60, 60, 60, 70, 70, 80, 90

Inter quartile range (IQR) = Upper quartile(Q3) - Lower quartile(Q1)

Let us arrange the data in ascending order, we get

40, 50, 60, 60, 60, 70, 70, 80, 90

The lower half data is

40, 50, 60, 60

Median (Lower quartile (Q1)) = $\frac{50+60}{2}$

= $\frac{110}{2}$ = 55

The upper half data is

70, 70, 80, 90

Median (Upper quartile (Q3)) = $\frac{70+80}{2}$

= $\frac{150}{2}$ = 75

Inter quartile rane = Upper quartile - Lower quartile

= 75 - 55

= 20

Hence, inter quartile range of the given data is 20.