The distribution below gives the weights of 30 students of a class. Find the median weight of the students.

Weight (in kg)	Number of students
40 - 45	2
45 - 50	3
50 - 55	8
55 - 60	6
60 - 65	6
65 - 70	3
70 - 75	2

Cumulative frequency distribution table is as follows :

Here, n = 30, $\dfrac{n}{2} = \dfrac{30}{2} = 15$.

Cumulative frequency just greater than 15 is 19, belonging to class-interval 55 - 60

∴ Median class = 55 - 60

Class size (h) = 5

Lower limit of median class (l) = 55

Frequency of median class (f) = 6

Cumulative frequency of class preceding median class (cf) = 13

By formula,

Median = $l + \Big(\dfrac{\dfrac{n}{2} - cf}{f}\Big) \times h$

Substituting values we get :

$\Rightarrow \text{Median } = 55 + \dfrac{15 - 13}{6} \times 5 \\[1em] = 55 + \dfrac{10}{6} \\[1em] = 55 + 1.67 \\[1em] = 56.67$

Hence, median weight = 56.67 kg.