Median is the middle value of the series. It
is also called 50^{th} percentile or
second quartile.
Individual series:

First arrange the series the series in
ascending or descending order.

If the number of values is odd then
If number of values is even then
Where N = number of items
Example: To find the median of 1,2,5,7,3,6,4
Arrange the series in ascending order
1,2,3,4,5,6,7
N = 7
= 4^{th} value = 4.
Discrete series:

First arrange the series in ascending or
descending order.

Find commulative frequency.
N = Number of items
Example: To find the median of
Value 
Frequency 
Commulative frequency 
2 
1 
1 
3 
5 
6 
4 
10 
16 
5 
15 
31 
= 16^{th} value
= 4
Continuous Series:

First find commulative frequency.

Find median class by using the formula N
/ 2.
Where l_{1 }= lower limit of median
class
l_{2} = upper limit of median class
N = Number of items
c = Commulative frequency of class
preceeding median class
f = Frequency of median class.
Example: To find the median of
Marks 
Frequency 
Commulative frequency 
10 – 20 
10 
10 
20 – 30 
15 
25 
30 – 40 
20 
45 
40  50 
30 
75 
Here N / 2 = 75 / 2 = 37.5
Therefore median class is 30 – 40
l_{1} = 30, l_{2} = 40, c =
25, f = 20
= 36.25
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