7.2.4 Interquartile Range of Grouped Data

Interquartile Range of Grouped Data (without Class Interval)

Example 2:

The table below shows the marks obtained by a group of Form 4 students in school mid-term science test.

Determine the interquartile range of the distribution.

Solution:

Lower quartile, Q₁= the

\frac{1}{4} {(24)}^{th}

observation

= the 6^thobservation

= 2

Upper quartile, Q₃= the

\frac{3}{4} {(24)}^{th}

observation

= the 18^thobservation

= 4

Interquartile Range

= upper quartile – lower quartile

= Q₃– Q₁

= 4 – 2

= 2