Stacking advantage: doing the math

[Morrus]

It's important to note in the RAW that I think we're meant to read Advantage and Disadvantage as conditions, not currencies -- you don't build up more than one. And advantage and disadvantage cancel each other out.

So, if you have advantage from three sources, you have advantage. If you have advantage from three sources and disadvantage from one, they cancel each other out (it doesn't require three sources of disadvantage to counter three sources of advantage).

You are correct; that is how it currently is. That's why my suggestion is a suggestion.

 

[Radiating Gnome]

You are correct; that is how it currently is. That's why my suggestion is a suggestion.

Sorry; didn't mean to misrepresent what you were saying. I was mostly making a point of saying it out loud for my own sake -- I'm the sort of rogue-loving player and DM who would try to argue it didn't work that way if I'm not careful to make sure I'm clear on it myself.

Some days, especially when I haven't had enough coffee, I'm a dope.

 

[Dragoslav]

I was just thinking over breakfast about whether it would be feasible to let advantage/disadvantage stack.

The chance of one success from 1 dice is: 60%
The chance of one success from 2 dice is: 84%
The chance of one success from 3 dice is: 93%

I'll agree that 3 dice makes the chance of success obscenely high, but maybe that's not a bad thing? How often would someone be able to get 3 advantages, anyway, and shouldn't they be rewarded for doing so?

On the other hand, that also means that enemies could stack up disadvantages on you.

So it seems like it would make combat very, very swingy.

EDIT: Forgot to mention that, in 4e at least, there are characters (primarily rogues) who can already hit on a d20 roll of 2 under optimal conditions. So Maybe letting (dis)advantage stack wouldn't produce unheard of results, but would be a more streamlined way of doing it than trying to keep track of all of your +1 and +2 bonuses?

 

[Kinak]

So from three dice onwards, we're looking at near certainty? Yeah, that does sound too much. I was hoping the diminishing returns would be more pronounced.

Well, that's with a 60% base success. So you need to roll a 9 or higher. In a bonus-based system, that would be like giving +7 total modifier, which I don't think is really out of line.

If you take it's evil twin, 40% chance of success, you end up with:
0: 40%
+: 64%
++: 78%
+++: 87%
++++: 92%

So you're looking at some pretty good diminishing returns: +5, +3, +2, +1

When you really need to bust out, the 20% chance of success, you get:
0: 20%
+: 36%
++: 49%
+++: 59%
++++: 67%

Still good diminishing returns: +3, +3, +2, +1

I think you'd be on pretty solid ground mathematically, compared to handing out similar bonuses. Also, less math, which I find speeds things up considerably.

It can trivialize simple tasks, even moreso than straight bonuses because it washes out natural 1s, but it takes an awful lot of advantage to tackle a difficult roll.

Personally, I'll be sticking with the teeter-totter (one advantage/disadvantage), so I can hand advantages out like candy and not worry about forgetting some once we've overcome disadvantages.

Cheers!
Kinak

 

[Kzach]

What IS the effective bonus of rolling twice? I had always thought it was 2.5 but I've seen people saying it's around 3-4.

 

[Chris_Nightwing]

If you cancel them out on a 1-for-1 basis, but only ever allow one extra dice, that could work. More than 2 dice starts to get silly though.

I guess it depends whether you think attacking a blind, prone target from hiding can be cancelled because it's foggy, or whether you also need to be stunned and drunk.

I note that they didn't fold cover into the dis/ad rules and are in fact using the +2/+5 version of 4 rather than +2/+4 version of 3e. I am all for reduced maths, but it feels like some things ought to be straightforward bonuses/penalties.

 

[Danzauker]

If I'm not mistaken, this ia a table showing the percentages of success on a target number 1 to 20, for "No advantage" to "Triple advantage".

1 100.00% 100.00% 100.00% 100.00%
2 95.00% 99.75% 99.99% 100.00%
3 90.00% 99.00% 99.90% 99.99%
4 85.00% 97.75% 99.66% 99.95%
5 80.00% 96.00% 99.20% 99.84%
6 75.00% 93.75% 98.44% 99.61%
7 70.00% 91.00% 97.30% 99.19%
8 65.00% 87.75% 95.71% 98.50%
9 60.00% 84.00% 93.60% 97.44%
10 55.00% 79.75% 90.89% 95.90%
11 50.00% 75.00% 87.50% 93.75%
12 45.00% 69.75% 83.36% 90.85%
13 40.00% 64.00% 78.40% 87.04%
14 35.00% 57.75% 72.54% 82.15%
15 30.00% 51.00% 65.70% 75.99%
16 25.00% 43.75% 57.81% 68.36%
17 20.00% 36.00% 48.80% 59.04%
18 15.00% 27.75% 38.59% 47.80%
19 10.00% 19.00% 27.10% 34.39%
20 5.00% 9.75% 14.26% 18.55%

 

[Neonchameleon]

What IS the effective bonus of rolling twice? I had always thought it was 2.5 but I've seen people saying it's around 3-4.

Depends what your target number is. For instance if you have a 50% to hit chance on one dice it becomes 75% on two - you need to fail both - so it's a +5 at this point. On the other hand if you need a 20 to hit then your chance moves from 1/20 to 39/400 or just under the effect of a +1. Likewise if you need a 2 to hit it's just under the effect of a +1.

There's more math in the other thread on the subject if you want the exact numbers, but 2.5 assumes that a natural 20 is needed as often as an 11 to hit - which it hasn't been in any game I've ever played. If you need a natural 20 you probably want to run away instead. The 3-4 estimate is based on a more common range of task difficulty.

 

[Dizlag]

Does rolling two d20s for an attack / check and taking the best still feel like D&D to you all? I would be curious to see what the actually bonus is, if the +3 or +4 is correct then I personally, would prefer this method.

You could "stack advantages" this way if you'd like by saying if you have one advantage the bonus would be a +3 and two or more advantages would grant a +4 advantage.

For instance, if I brace my crossbow, but the defender is prone ... no advantage. However, if I brace my crossbow and aim with the defender prone it would be a +3 advantage. If I brace my crossbow, aim for a round, and hide with the defender not having a clue then the advantage could be +4.

Thoughts?

Dizlag

 

[Neonchameleon]

Double Post