Here, we can see that the intervals are unequal.
Firstly, we convert the unequal class intervals into equal class intervals.
We have n = 80
So, n/2 = 80/2 = 40
The cumulative Frequency just greater than n/2 is 45 then the median class is 12-18 such that
the lower limit (l) = 12
cumulative frequency of the class preceding 12 – 18 (cf) = 17
frequency of the median class 12 – 18 = 28,
class size (h) = 6
Using the formula,
