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

Weight (in kg) | Number of students(Frequency) | Cumulative Frequency
40 - 45 | 2 | 2
45 - 50 | 3 | 5
50 - 55 | 8 | 13
55 - 60 | 6 | 19
60 - 65 | 6 | 25
65 - 70 | 3 | 28
70 - 75 | 2 | 30
=n
We have, n=30
n/2=15
The cumulative frequency just greater than n/2 is 19 and the corresponding class is 55-60.
Thus, 55-60 is the median class such that n/2=15, l=55, f=6, cf=13, and h=5
Substituting these values in the formula
Median, M = l + \frac{\frac{n}{2} - cf}{f} \times h
M = 55 + \frac{15 - 13}{6} \times 5
M = 55 + \frac{2}{6} \times 5 = 55 + 1.67 = 56.67
Hence, the median weight = 56.67 kg.