It seems like it should be possible to calculate the mean (usual average) from a 5-number summary of a set of numbers (min, first quartile or Q1, median, third quartile or Q3, and max). You should be able to calculate roughly what a percentile is, then by taking each discrete percentile and then taking the average of those hundred numbers... or better yet by using calculus and taking every percentile point, and the average of every point, you should be able to come really close to the mean, if not compute it directly. I, however, don't know math well enough to do that, nor do I remember any calculus. In one data set that I'm looking at, the min, Q1, median, Q3, and max are: 0, 3900, 18882, 50145.5, 1250000 And the mean is: 46172.04545 or just under Q3. How can the mean be calculated from those 5 numbers?