Write the median class of the following distribution:
Class | 0 - 10 | 10 - 20 | 20 - 30 | 30 - 40 | 40 - 50 | 50 - 60 | 60 - 70 |
Frequency | 4 | 4 | 8 | 10 | 12 | 8 | 4 |
To find median class,
Assume Σfi = N = Sum of frequencies,
fi = frequency
and Cf = cumulative frequency
Lets form a table.
AGE(years) | NUMBER OF PATIENTS(fi) | Cf |
0 - 10 | 4 | 4 |
10 - 20 | 4 | 4 + 4 = 8 |
20 - 30 | 8 | 8 + 8 = 16 |
30 - 40 | 10 | 16 + 10 = 26 |
40 - 50 | 12 | 26 + 12 = 38 |
50 - 60 | 8 | 38 + 8 = 46 |
60 - 70 | 4 | 46 + 4 = 50 |
TOTAL | 50 |
So, N = 50
⇒ N/2 = 50/2 = 25
The cumulative frequency just greater than (N/2 = ) 25 is 26, so the corresponding median class is 30 - 40.
Hence, median class = 30 - 40