### Topic Page: Quartile (Statistics)

**quartile**

*The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide*

In statistics, any one of the three values that divide data into four equal parts. They comprise the lower quartile, below which lies the lowest 25% of the data; the median, which is the middle 50%, half way through the data; and the upper quartile, above which lies the top 25%. The difference of value between the upper and lower quartiles is known as the interquartile range, which is a useful measure of the dispersion of a statistical distribution because it is not affected by freak extreme values (see range). These values are usually found using a cumulative frequency diagram.

For example, a football team scored the following goals in one season:

This information can be displayed in a cumulative frequency curve:

From the curve, the median is 2.4 goals, the lower quartile is 1.2 goals, and the upper quartile is 3.4 goals. The interquartile range is 3.4 − 1.2, which is 2.2 goals.

The lower quartile may also be described as the 25th percentile; the median as the 50th percentile; and the upper quartile as the 75th percentile.

essays

Cumulative frequencies and medians

weblinks

Box and Whiskers Plots

### Related Articles

##### Full text Article Percentiles

The percentile is a concept often used to summarize data and place the score or measurement taken on an individual into the context of a larger...

##### Full text Article quartile

Any of the three points that divide a distribution or set of observations into quarters, or four equal parts. The first quartile (Q1, or...

##### Full text Article decile

The value obtained from a set of data arranged in order of magnitude by dividing it into ten equal parts. The first, or lowest, decile is sometimes