QUOTE (Bobson @ Nov 13 2008, 05:14 PM)

If rolling with edge included adds 40% or more to your dice pool (i.e. 4 or more edge when you have 10 dice to begin with), then if you're going to spend edge either way, it's always better to spend the edge up front. On the other hand, the whole point of being able to reroll failures is that you don't *have* to spend the edge, so it goes back to being a judgement call. How much chance of success is the chance of preserving your Edge worth?

Okay, the rest of the calculation.

In a lot of cases N*5/9 is going to be more than (N+M)*0.4.

Multplying through and subtracting. the condition is that

N*7/45 > M*0.4

Remember that N is your total dice pool, and M is your edge.

Obviously, for small pools, adding edge dice and exploding is better than rerolling failures. But, if we expand the formula, we find that rerolling failures is better if

N*7 > M*18

Now, if you have 3 edge dice, that means you are better off rerolling failing dice if you have 8 or more dice in the pool.

Even with 5 edge dice, you are better off rerolling failures if your pool is 13 or more dice.

(And that is ignoring the beneift of not using the edge if you roll well in the first place, as well as some other second order effects that make rerolling failed dice somewhat better.)

Yours,

Joel

PS: The big thing to remember about Shadowrun dice is the standard deviation. Unless the GM allows the rule of 4, there is tremendous variation in the results of rolls. That appears to be intentional, and may well be a good thing.