Glossary term
Quartile: Meaning and Definition
Reviewed and approved by Dr. Anamika ShrivastavaPublished Last updated
Quartiles are the three values that divide a set of ordered data into four equal parts. The first quartile, Q1, has 25 per cent of the items below it; the second, Q2, is the median; and the third, Q3, has 75 per cent below it. Q1 and Q3 enclose the middle half of the data.
In more detail
Quartiles show the spread as well as the centre of the data. The gap between Q3 and Q1, the interquartile range, covers the middle 50 per cent and is not affected by extreme values. Percentiles divide the data into 100 parts, so Q1 is the 25th percentile and the median is the 50th.
Example
For ordered values 40, 42, 47, 48, 51, 55, 57 and 60, Q1 is 43.25 and Q3 is 56.5.
Key points
- Q1 is at the (N + 1) ÷ 4 th item.
- Q3 is at the 3(N + 1) ÷ 4 th item.
- Positional measures like the median.
Common mistake
Finding quartiles without first arranging the data in order.
Related terms
Where it is explained
This term is explained in Class 11 Statistics Chapter 5: Measures of Central Tendency.