Finding Quartiles and Median of a List of Numbers

To find the median and quartiles of a list of numbers,first sort them – if they are not already sorted. If there are nnumbers in the list:

The median will be thethnumber . If this is not a data point –iseven – find the averare of thethandthnumber .

If the ordered list is

2, 2, 3, 4, 4, 5, 5, 5, 6, 6, 7, 7, 8, 8, 8, 9, 10, 11

There are 18 numbers in the list.

The 9 ^th number is 6 and the 10 ^th number is 6. The average of these is 6 so the meduan is 6.

To find the lower quartile, calculateandround up to the nearest whole number.

whichrounds up to 5. The 5 ^th number in the list is 4 so thelower quartile is 4.

To find the upper quartile, calculateandround up to the nearest whole number.

whichrounds up to 15. The 15 ^th number in the list is 8 so theupper quartile is 4.

There is much confusion about how to calculatequartiles because many textbooks have different method. Always checkwith your teacher.