# Deciles and Percentiles

__Deciles__

Deciles are the partition values which divide the set of observations into ten equal parts. There are nine deciles: . The first decile is , which is a point which has 10% of the observations below it.

__Deciles for Individual Observatio__ns (Ungrouped Data)

__Quartile for a Frequency Distributio__n (Discrete Data)

__Quartile for Grouped Frequency Distribution__

__Percentiles__

Percentiles are the points which divide the set of observations into one hundred equal parts. These points are denoted by , and are called the first, second, third... ninety ninth percentile. The percentiles are calculated for a very large number of observations like workers in factories and the populations in provinces or countries. Percentiles are usually calculated for grouped data. The first percentile denoted by is calculated as . We find the group in which the item lies and then is interpolated from the formula.