Stacking advantage: doing the math

[The Red King]

I say they should all stack.

But then again, whatever the players can do, their adversaries can do as well.

 

[Morrus]

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



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?.

I'm kinda with you there. If you've made the effort and arranged a situation so as to make your task incredibly easy, then it should be incredibly easy. That's certainly how people operate in the real world!

 

[Kinak]

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.

It depends. Mathematically, it comes out to 3.325 but that doesn't really reflect the effect on gameplay.

If you were rolling damage dice twice and keeping the higher, the average bonus would mean something, since every +1 is a hit point of damage.

But since you're just trying to beat a target number, the effect actually varies based on that target. If you'd need to roll a 20 normally, that's about 5% more likely (similar to a +1). If you'd need to roll an 11 normally, that's about 25% more likely (similar to a +5).

If it were equally likely you'd need to roll a 20 to hit or a 2 to hit as an 11, the number would be that 3.325, but most games don't throw things like that at you frequently. So, in play, the bonus is more around +4, but that will vary based on the challenges you're facing.

More discussion (and graphs) here.

Cheers!
Kinak

 

[IronWolf]

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?

I think in actual play it would be frustrating trying to remember all the bonuses and stacking them. I'd have to see it in actual play though, but that is my suspicion.

 

[Kzach]

Not meaning to derail the thread but also thinking it's not worth starting another thread but I'm curious to know if the chance of rolling a critical hit (20) is increased when rolling for advantage. Primarily I'm curious because that was my understanding with the Avenger mechanic and one of the reasons why there were 'crit-fisher' builds.

If so, then that makes rogues pretty damn awesome.

 

[IronWolf]

[MENTION=90804]OnlineDM[/MENTION] did nice write up on his blog I thought on the math of advantage and disadvantage:

Advantage and Disadvantage in D&D Next: The Math | Online Dungeon Master

 

[Warbringer]

We've been using a dice pool concept for a few years in our 3e hybrid game.

PCs have a base pool of two dice plus one based on initial class for specific actions: fighters - combat; spell casters - casting; rogues - skill checks.... Feats grant situational bonuses as well, such as combat advantage ... these are spend on actions, either for d20 checks or movement (cost d20 standard movement, 2d20 run)

Players choose what they want to do in a round: no movement, want to attack, extra defense (1d20 attack, 2d20 defend ( we use the old active check concept from UE))

We usually see 2 dice in a key action check, 3 when it's a desperation move... Yes it leads to more successes, against the curves seen, but the players love the control and it has created numerous dramatic outcomes.. Most fun.

Point is, the complexitybof the math disappears very quickly as players get a gut feel for the likelihood os success.

This is a nice mechanical change

 

[Crazy Jerome]

I can sort of see room for a two-tier stack, in the way that some games will use a two-tier critical system (i.e. crits and then super crits). But past that point, the diminishing returns aren't going to make it worth the hassle, in most situations.

So you end up with a protocol something like this, maybe:

1. If you have 2 or more advantages and no disadvantages, you get 3 dice.
2. If you have more advantages than disadvantages, you get 2 dice.
3. Otherwise, you get 1 die.

Then do the parallel setup for disadvantages being the greater thing. That leads to 5 possibilities:

• Aargh! (multiple disadvantage, no advantage)
• Disadvantaged
• Standard
• Advantaged
• Woo Hoo! (multiple advantage, no disadvantage)

That covers a hefty chunk of the times when the situation is great or pear-shaped, without getting into all of the fiddly details of dealing with something like the difference between a 3:1 or 4:1 advantage/disadvantage ratio. And for that matter, it's not difficult to add such an extension to the current rule as an option, as it still has a cap on how much it moves the probabilities.

Like a lot of situations in real life, getting to Woo Hoo! is as much about minimizing your weaknesses as maximizing your strengths.

 

[Rampaging Lawn Gnome]

Would you also stack disadvantage? I think I would. Shooting a crossbow at a hidden target while leaping over a pit while intoxicated should be difficult (rolling 3d20 take lowest). But does it tamper creativity?

 

[Kzach]

[MENTION=90804]OnlineDM[/MENTION] did nice write up on his blog I thought on the math of advantage and disadvantage:

Advantage and Disadvantage in D&D Next: The Math | Online Dungeon Master

So if I understand this correctly, then if I'm rolling to attack and I have advantage, then I have a 9.75% chance of rolling a critical hit instead of the standard 5% chance?

Cool.