istance between the 25th and the 75th percentile. A percentile is a value such that a specified proportion of the values are lower than it. So the 25th percentile is the lowest value in the data such that 25% are even lower. If you go back to the definition of the median, you may notice that the median is actually the 50th percentile. The 25th, 50th, 75th and 100th percentiles are also respectively called the 1st, 2nd, 3rd, and 4th quartile, hence the name inter-quartile range. To compute percentiles, it is