Dividing a statistical group into five categories results in quintiles. To divide the group, choose a variable upon which to base the division. For example, if dividing a high-school class for ranking purposes, you could rank grades by fifths, inserting students into each quintile based on grades.
Quintiles are used by a number of colleges, universities and testing services to determine where students fall in class rankings. Students in the top quintile are typically those with the highest grades or best test results. Those at the bottom are usually those who have not fared as well on tests or classroom assignments. These rankings are often used to determine college admission.
The quintile ranking system is commonly used to determine the performance of companies. Whether the ranking is based on profits, stock price or growth, users of these data can see which companies rank in the top 20 percent of the industry and which companies rank lower. These data are often separated into groupings to show which companies have strong balance sheets on a number of factors.
In Missouri, public aid rates are separated into quintiles based on the relative size and wealth of each of the state's counties. This allows administrators to ensure that rates are distributed evenly to those most in need in a way that reflects the general wealth or poverty of a specific region.