Simplify the following text for a Grade 6 native English-speaking person.
Original: The Percentile is a measurement in statistics . To find a certain percentile , a frequency distribution of the results is done - they are ranked .
Simplified: Thus , rounding to two decimal places , â ' 3 is the 0.13 th percentile , â ' 2 the 2.28 th percentile , â ' 1 the 15.87 th percentile , 0 the 50th percentile ( both the mean and median of the distribution ) , +1 the 84.13 th percentile , +2 the 97.72 th percentile , and +3 the 99.87 th percentile .