Quartile: Definition and Example

Definition of Quartile

A quartile is a statistic describing how a set of data points are divided into 4 groups. Quartiles split a set of data by using 3 points: the lower quartile (Q1), the median (Q2), and the upper quartile (Q3). Together with the minimum and maximum values, 3 quartiles split the data set into 4 equal groups:

• 1^st group: from the minimum to the lower quartile (Q1)
• 2^nd group: from Q1 up to the median (Q2)
• 3^rd group: from the median (Q2) to the upper quartile (Q3)
• 4^th Group: from Q3 to the maximum data point.

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Rules and steps for finding Quartiles

1. Finding median (also called Q2, second quartile)

The median is the midpoint (or middle value) of a set of numbers. You can find the median by ordering the set of numbers and then finding the middle value in the set. The median is also called the 2^nd quartile or Q2.

2. Finding the lower quartile (also called Q1, first quartile)

• Step 1: You can find the lower quartile by putting the set of data in order, then locating the median value.
• Step 2: After finding the median value, you can find the middle value between the minimum and the median.

3. Finding the upper quartile (also called Q3, third quartile)

• Step 1: You can find the upper quartile by putting data points in order, then finding the median value.
• Step 2: After finding the median value, you can find the middle value between the median and the maximum.

Finally, you will get 3 quartile values, 77 (lower quartile, Q1), 81 (median, Q2), and 89 (upper quartile, Q3).