volatility

How can I measure volatility?

I am trying to determine the volatility of a rank. More specifically, the rank can be from 1 to 16 over X data points (the number of data points varies with a maximum of 30). I'd like to be able to measure this volatility and then map it to a percentage somehow. I'm not a math geek so please don't spit out complex formulas at me :) I...

reference assignment is atomic so why is Interlocked.Exchange(ref Object, Object) needed?

In my multithreaded asmx web service I had a class field _allData of my own type SystemData which consists of few List<>s and Dictionary<>s marked as volatile. The system data (_allData) is refreshed once in a while and I do it by creating another object called newData and fill it's data structures with new data. When it's done I just as...