Before you understand What is Median ?
You must know:
What is Ascending Order ?
What is Descending Order ?
Definition
In a given set of observation, after arranging in ascending or descending order, the middle observation which divides the set of observation in two equal parts is referred to as Median.
In order words, Median refers to the value which lies in the middle of the set of data, which is arranged in ascending or descending order.
** Note  While finding Median only those cases are considered, where the value number of observation in a given set of data is ODD.
Steps to find Median in a given set of observations or data:
Step 1  Arrange the given set of observations or data in ascending or descending order.
Step 2  Find the middle value, which divides the given data in two equal parts.
Step 3  The resultant value is the Median of the data.
For further understanding let's try following examples:
Example 1  Following data represents weight of 11 students in a class. Find Median.
35, 29, 37, 38, 41, 36, 42, 47, 39, 40, 48
Answer  Follow the steps as explain above :
Step 1  Arrange the given set of observations or data in ascending order and we get;
29, 35, 36, 37, 38, 39, 40, 41, 42, 47, 48
Step 2  Find the middle value, which divides the given data in two equal parts.
29, 35, 36, 37, 38, 39, 40, 41, 42, 47, 48
You can see value 39 is the middle of set of data and divides the given data in a two equal groups comprising 5 values each.
Step 3  Hence, 39 is the Median of the data.
Example 2  Following data represents score of 15 students in a science. Find Median.
75, 80, 91, 76, 82, 93, 78, 83, 94, 84, 96, 79, 87, 89, 90
Answer  Follow the steps as explain above :
Step 1  Arrange the given set of observations or data in descending order and we get;
96, 94, 93, 91, 89, 90, 87, 84, 83, 82, 80, 79, 78, 76, 75
Step 2  Find the middle value, which divides the given data in two equal parts.
96, 94, 93, 91, 89, 90, 87, 84, 83, 82, 80, 79, 78, 76, 75
You can see value 84 is the middle of set of data and divides the given data in a two equal groups comprising 7 values each.
Step 3  Hence , 84 is the Median of the data.

