Quartile is often used to draw box charts in statistics. It is a set of sorted values for 25% and 75% positions. Quartile is to divide all data into four parts with three points, and each part contains 25% data.
Obviously, the middle quartile is the median, so the quartile usually refers to the value in the 25% position (called the lower quartile) and the value in the 75% position (called the upper quartile).
Similar to the calculation method of median, when calculating quartile according to ungrouped data, the data are sorted first, and then the position of quartile is determined, and the value of this position is quartile.
Different from the median, there are several methods to determine the position of quartile, and the results of each method will be different, but the difference will not be great.