 This is an example on how to calculate a percentile. Keep in mind there are many ways to calculate a percentile, so this is just one of the many ways. In my Lucky Charms example here, I collected a number of marshmallows and 40 different boxes. I recorded the information in the table. I want to find the 25th percentile, meaning I want to find the data value of 25% of the data, less than or equal to it. So I'm going to take 40 and multiply by 25% over 0.25, which gives me a whole number 10. What I'm finding here is my locator. And you may think that because I got 10 that I want the data value in the 10th location in the data set. However, this is not the case. Anytime you get a whole number for your locator, you must take the average of the data value in the found position. So 10th position and the next bad data and the next position that follows. So take the average of the 10th and 11th data value. So that means my 25th percentile would be an average of 130 plus 133. That is my data value in the 10th position, data value in the 11th position. And we will divide by two since we are taking an average of two values. So 263 over 2, which gives me 131.5. The 25th percentile in this case is 131.5. So once again, just because we got a whole number for our percentage of our sample size 40 does not mean that we take the 10th data value. We take the average of the 10th and the average of the 11th. So we add them up divide by two and we got 131.5.