Question :
| Weight in (kg) | 40 – 45 | 45 – 50 | 50 – 55 | 55 – 60 | 60 – 65 | 65 – 70 | 70 – 75 |
| Number of students | 2 | 3 | 8 | 6 | 6 | 3 | 2 |
Solution :
We prepare the following table to compute the median :
| 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 | 38 |
| 70 – 75 | 2 | 30 |
We have : n = 30, So, \(n\over 2\) = 15
The cumulative frequency just greater than \(n\over 2\) is 19 and the corresponding the class is (55 – 60).
Thus, (55 – 60) is the median class such that \(n\over 2\) = 15, l = 55, f = 6, cf = 13 and h = 5.
Substituting these values in the formula,
Median = l + (\({n\over 2} – cf\over f\))(h)
= 55 + (\(15 – 13\over 6\))(5) = 55 + \(2\over 6\)(5) = 55 + 1.67 = 56.67
Hence, the median weight is 56.67 kg