[PvK]

These are good formulae if you know enough math to appreciate what they are saying as a general principle. In practice though, you almost never have a reliable figure for enemy's chance to hit you, and even if you had full information, it's not a single number, but a probablility distribution, and a different one for each enemy design, experience level, weapon, etc.

So, this illustrates the theory, and would be a reasonable system for an improved AI to use, and if you're really confused and think this will help your designs, it'll give you something to give you advice, but there isn't really a valid formula that will tell you what the best thing to do is.

PvK