Example:
Set of data: 1,2,3,4,5,6,7,8
Cross of 1 and 8, cross off 2 and 7, cross off 3 and 6. Two numbers are left so find the average by adding the two numbers and dividing by 2.
i.e. 4+5=9 and 9/2= 4.5
The median would be 4.5.
In other words the median is halfway between the two numbers.