Percentiles & Quartiles

Common Percentile Questions (FAQ)

This video introduces percentiles, and covers a few of the most common confusions you'll come across. It also raises the question of which definition your teacher uses, an important question because you don't want to be using a different one than your professor!

Calculating Percentile of a Data Point

This is the "forward" percentile problem, where you're given a list of numbers and asked to find the percentile of a given value. This video covers the trickier wording that sometimes disguises these problems, as well as how to deal with the two most common definitions of percentiles.

Percentiles & Quartiles On Your Calculator

Will your calculator magically tell you the percentile of a value? Not really. Will it tell you the quartiles? You betcha!

Percentiles In Reverse: Given a Percentile, Predict The "Cutoff"

This type of problem is the one with all the crazy instructions: "If L is a whole number, take the average of the Lth and L+1th value, but if L is a decimal always round up!" You get the idea. If they give you a list of numbers and ask you where the 60th percentile would be, this video is for you.


Quartiles are just a special case of percentile where the percentiles in question happen to be 25, 50, and 75. Unfortunately, that means you'll get burned by all the craziness of reverse percentile problems, but on the bright side your calculator will spit out quartiles with ease!