Quartiles

Quartile is another term referred to in percentile measure. The total of 100% is partitioned in three places, Q1, Q2, and Q3.

  • Lower Quartile is the 25th percentile.  (0.25)
  • Median Quartile is the 50th percentile. (0.50) 
  • Upper Quartile is the 75th percentile.  (0.75)

Example:

Test Scores Frequency Cumulative Frequency
76-80

3

3

81-85

7

10

86-90

6

16

91-95

4

20


The total frequency is 20.
The quartile information for this data is:

Lower Quartile    0.25 · 20   =    5   The lower quartile falls in the interval  81 – 85. 
Median Quartile   0.50 · 20   =   10   The median quartile falls in the interval  81 – 85.
Upper Quartile   0.75 · 20    =   15  The upper quartile falls in the interval  86 – 90.

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