## About This Tool

The online Quartile Calculator is used to calculate the first quartile, second quartile and third quartile of a set of numbers.

## Quartile

In descriptive statistics, a quartile, a type of quantile, is one of three points that divide a data set into four equal groups, each representing a fourth of the distributed sampled population. There are three quartiles: the first quartile (Q1), the second quartile (Q2), and the third quartile (Q3). The first quartile, also called lower quartile, is equal to the data at the 25th percentile of the data. The second (middle) quartile is another name for the median of a data set. The third quartile, also called upper quartile, is equal to the data at the 75th percentile of the data.

## Calculating Quartiles

There are several different methods for calculating quartiles.^{[1]} This calculator uses a method described by Moore and McCabe to find quartile values. The same methord also used by The TI-83 to calculate quartile values. With this method, the first quartile is the median of the numbers below the median, the third quartile is the median of the numbers above the median.

## References

- http://mathworld.wolfram.com/Quartile.html