Yay math-hammer!
If you want to break things into raw percentage, then here's how it goes.
Imperial Guardsmen fire 100 lasgun shots at a T4 model with a 2+ armor save.
50 Lasgun shots hit.
16.67 (17) wound.
2+ armor saves roughly 84% of the time.
Of those 17 wounds, 13 save, so there are four casualties.
HOWEVER
The dice gods are utterly and completely fickle, and Nixon said it best: There are lies, damn lies, and statistics. I've seen ten conscripts kill five terminators with rapid-firing lasguns. Similarly, the other week, I shot five bolters at 24'' against Deathwing Terminators, hit five times, wounded five times, and then saw (you guessed it!) five ones. Don't read too much into the statistics. While they're generally good to go on, if you make someone roll enough dice, especially Chessex dice (which are rather poorly made, as research has shown, and come up on a 1 something like 28% of the time instead of the 16.667% that a theoretically perfectly balanced die will have for each facing), terminators WILL die.
Statistics are, in my experience, far more useful for breaching armour and dealing with close combat, where there are very little or large enough numbers of dice being thrown to actually see the statistics come into play. When you have ten guardsmen shooting at 12'' out, there aren't really enough dice to get a good sample to weigh against the statistics.
