Solution:
Here,
Preparing a cumulative frequency table to calculate median from the given data, we get
Class (X) | Frequency (f) | Cumulative frequency (cf) |
40-50 | 7 | 7 |
50-60 | 8 | 7+8=15 |
60-70 | 6 | 15+8=21 |
70-80 | 5 | 21+5=26 |
80-90 | 4 | 26+4=30 |
N=30 |
Using formula,
Median (Md) = The value of (N/2)th item
= (30/2)th item
= 15th item
here,
The corresponding class of cf 15 is 50-60
∴ Median class = 50-60
Again, by formula
Actual median (Md) = \(L+\frac{\left(\frac{N}{2}-cf\right)}{f}\cdot i\)
Where,
L = 50,
N/2 = 15
cf = 7
f = 8
i = 10
So, Actual median (Md)
= \(50+\frac{\left(15-7\right)}{8}\cdot10\)
= 60
∴ Median of the given data is 60.