By drawing an ogive; estimate the median for the following frequency distribution :

Weight (kg)	No. of boys
10 - 15	11
15 - 20	25
20 - 25	12
25 - 30	5
30 - 35	2

Cumulative frequency distribution table :

Here, n = 55, which is odd.

By formula,

Median = $\dfrac{n + 1}{2}\text{ th term} = \dfrac{55 + 1}{2} = \dfrac{56}{2}$ = 28th term.

Steps of construction of ogive :

1. Take 2 cm = 5 units on x-axis.

2. Take 1 cm = 10 units on y-axis.

3. Plot the point (10, 0), as ogive always starts on x-axis representing the lower limit of the first class.

4. Plot the points (15, 11), (20, 36), (25, 48), (30, 53) and (35, 55).

5. Join the points by a free hand curve.

6. Draw a line parallel to x-axis from point A (frequency) = 28, touching the graph at point B. From point B draw a line parallel to y-axis touching x-axis at point C.

From graph, C = 18.4

Hence, median = 18.4