Let us find the m

The data given in the question is inclusive type of data, we need to convert it into exclusive type of data.

In order to convert it to exclusive type of data, subtract 0.5 from the lower limit of class interval and add 0.5

To find median of data, we need to make a table calculating cumulative frequency.

For median:

We have, total frequency, N = 30

N/2 = 30/2 = 15

Observe, cf = 18 is just greater than 15.

Thus, median class = 15.5 – 20.5

Median is given by

Where,

L = Lower class limit of median class = 15.5

N/2 = 15

cf = cumulative frequency of the class preceding median class = 11

f = frequency of the median class = 7

h = class interval of the median class = 5

Substituting these values in the formula of median, we get

⇒

⇒ Median = 15.5 + 2.857

⇒ Median = 18.357

Thus, the median of data is 18.357.