>Whether this distance would be described as the total span encompassing all four numbers, or the maximum distance between any two of the four, I don't know. A

>Whether this distance would be described as the total span encompassing all four numbers, or the maximum distance between any two of the four, I don't know. Actually, either one would imply a bound on the other (although a slightly looser one). If you know the total span, the same number is a looser bound on the maximum between any two of the four, and if you know the maximum of any two, 3 times that gives you a loose bound on the total span.