Probability question

[Ogrork the Mighty]

Let's say a character has a 50% miss chance (from whatever). Can you just say that if the original attack roll is even, the attack misses and if it's odd then it calculates normally?

You'd be saving an extra roll...

 

[Particle_Man]

Hmmm...I think that might mess up some critical threat/critical hit stuff. If something crits on a nat. 20, then it doesn't ever crit, by your rule. But if you switch odd and even, then a weapon that crits on a 19-20 crits exactly as often as a weapon that crits on a 20 only.

So I would say it would need some more work.

 

[Lord Pendragon]

Let's say a character has a 50% miss chance (from whatever). Can you just say that if the original attack roll is even, the attack misses and if it's odd then it calculates normally?

You'd be saving an extra roll...

You'd be skewing things slightly depending on the target's AC. For instance, if the target has an AC of 20, you're effectively boosting his AC by 1 as well as giving him a miss chance. If the target's AC is 19, then things are fine.

Or so it seems.

 

[DemonAtheist]

wouldn't work, because sometimes there are only an odd number of die rolls that will hit. If you have to roll a 16 or better to hit, if you discard evens or odds, you either have a 2/5 or 3/5 chance...not 50/50

 

[brehobit]

While the proposal wouldn't be the same as the current rules (for reasons noted above) it is generally close enough I wouldn't worry about it. But I'd only do this if 50% miss chances come up a lot in your game...

 

[Lord Pendragon]

I usually just have the players roll percentage dice at the same time they roll their attack roll. A quick glance tells them if they're above or below 50%, then if they are above, they add up their attack bonus. It actually takes less time than a standard attack, since half the rolls skip any addition altogether.

 

[tarchon]

Let's say a character has a 50% miss chance (from whatever). Can you just say that if the original attack roll is even, the attack misses and if it's odd then it calculates normally?

You'd be saving an extra roll...

Do that but also take a natural 20 as a hit and it'll be close enough. 50% is fairly common because it's the miss chance for invisibility.

 

[tarchon]

wouldn't work, because sometimes there are only an odd number of die rolls that will hit. If you have to roll a 16 or better to hit, if you discard evens or odds, you either have a 2/5 or 3/5 chance...not 50/50

Yeah, but if half the cases are 2/5 and half are 3/5, it works out in the long run.

 

[Christian]

Yeah, but if half the cases are 2/5 and half are 3/5, it works out in the long run.

But half the cases aren't 2/5 and half 3/5. A 20 always hits, and 20 is always even; so whenever there are an odd number of 'successful' rolls, more than half will be even and less than half will be odd.

 

[Bauglir]

In the more extreme case, when a 20 is required to hit, this system would mean the creature is totally unhittable.