 This is an example on how to calculate a percentile. Keep in mind that there are multiple ways to calculating percentiles, so this is one of the many ways that are used. In my example, I have 40 boxes of lucky charms that were collected and the number of marshmallows counted in each. The information is recorded in the given table. Find the 31st percentile, meaning find the data value of 31% of the data less than or equal to it. So the first thing you wanna do is take your data sample size here, 40, and multiply by 31%, which means multiply by 0.31. 40 times 0.31 is 12.4. So I'm looking for the data value that's greater than or equal to 12.4 other data values. Well, I can't have four tenths of a data value, so I must round up, you always round up when you're finding percentiles, round up to 13. I need the 13th data value. So go to your sorted data, it has to be sorted in ascending order, and look for the 13th data value, 11, 12, 13. My 31st percentile is 137. 137 is my 31st percentile.