Usually, we don't only want to know the average or arithmetic mean of a set of values, which are sort of in the middle; we also want the extremes, the full range—the highest and lowest values. The sample data that we are using here already has those values per day—the high and low price. However, we need to know the highest value of the high price and the lowest price value of the low price. After all, how else would we know how much our Apple stocks would gain or lose?