Hypothetical - Stacking Dis/Advantage

[jjordan]

I know this has been discussed before but I can't find a thread on it.

Rolling with dis/advantage is the statistical equivalent of a -5/+5 modifier to a single die roll. What would the effective modifier of rolling 3d20 to resolve a 1d20 roll be?

[Unoriginal]

I know this has been discussed before but I can't find a thread on it.

Rolling with dis/advantage is the statistical equivalent of a -5/+5 modifier to a single die roll. What would the effective modifier of rolling 3d20 to resolve a 1d20 roll be?

-25/+25, as far as I'm aware.

[Man_Over_Game]

I know this has been discussed before but I can't find a thread on it.

Rolling with dis/advantage is the statistical equivalent of a -5/+5 modifier to a single die roll. What would the effective modifier of rolling 3d20 to resolve a 1d20 roll be?

It's a long and drawn out explanation as to why, but Dis/Advantage is worth about +/- 3.33 at worst, and a +/- 4.5 at best, so it ends up averaging out to about a +/- 4 overall. WotC only accounted for the values at the 50% mark (which is +/- 5, from +/- 4.5 rounded up).

But while the midpoint is where Dis/Advantage is worth the most, not all checks start with a 50% chance of success, so it's almost always less valuable than a +/- 4.5 difference. But rounding to 5 is pretty dang easy to remember, even if it does mean that Dis/Advantage are stronger as static numbers.



But to answer your question directly, assuming we're just basing it on the 50% chance difference between the different roll types (1d20, 2d20, 3d20), you're looking at a +4.5 from 1-to-2 dice, and a ~+2 from 2-to-3 dice.

So the value you'd probably want to modify a 3d20 roll with is +/- 7, although that probably is closer to +/- 6 after accounting for realism.


If I were to make it a rule, I'd just write it up as +/- 4 on the first die, and halve the value of the next additional die (so a 2d20 is worth 4, 3d20 worth another 2, 4d20 worth another 1).

[Greywander]

I think the value actually depends on what you need to roll, but the rules do say it counts as a +5 on passive checks. What I do know are that you get diminishing returns for each extra die you roll. Let's take a look at AnyDice (https://anydice.com/program/1de26) to see what some of the probabilities/average rolls are.

On a straight d20, you have a 50% chance of rolling 11 or higher.
With 2d20 take highest, you have a 51% chance of rolling 15 or higher.
With 3d20, 48.8% chance for 17 or higher.
With 4d20, 47.8% chance for 18 or higher.
With 5d20, 55.6% chance for 18 or higher.

So, to answer your question, 3d20 looks like it would translate to a +7.

[JackPhoenix]

Mean of 3d20, pick highest, is 15.49. Mean of 2d20, pick highest, is 13.82.
Mean of 3d20, pick lowest, is 5.51. Mean of 2d20, pick lowest, is 7.17.

3d20 is +5/-5.
2d20 is about +3/-3.

[Chronos]

The +5 isn't rounded: In the best case scenario, advantage is worth exactly as much as +5 to a die roll. It turns a 50% chance of success into a 75% chance of success, the same as a +5 would.

That said, you're right that that's only if you had exactly a 50% chance initially, and that's the best case for advantage. In the typical case, where your initial chance of success might or might not be 50%, advantage will be worth less (how much less depends on what you assume the "typical case" is).

It's also worth less on opposed checks than it is on checks vs. a DC. If both parties to an opposed check have the same modifier, then each one will have roughly a 50% chance of success (only roughly, not exactly, because it's possible for both to roll the same, and the tiebreaker will favor one of the parties). On the other hand, with equal bonuses but advantage on one side, then the advantaged party's chance will be approximately 2/3, because each of the three dice has an equal chance of being the highest one, and the advantaged party gets two of those three dice.

[KorvinStarmast]

Might be worth reviewing this analysis (https://rpg.stackexchange.com/q/14690/22566); the mean is sensitive to TN.

I'd suggest not going for the d20 dice pools approach.

For Unoriginal: I think +21/-21 might be a better fit, but good one.

[Boci]

I'm sure I've had this conversation before, but would a workable compromise be you still only ever roll 2d20, but multiple instances stack for the purpose of cancelling out the other? So if you had 3 sources of advantage and 1 source of disadvantage, you would still only rolld 2d20, but you would get advantage unlike the current RAW.

One objection to this houserule I recall is that it would encourage advantage hunting, but I've never been convinced by it. Players are already incentivized to get advantage, and nor is it that easy, so whilst 2 sources of advantage could be worthwhile with this houserule, they will only be so if you have disadvantage. On a regular attack roll the two sources offer no benefit.

[Kyutaru]

Allowing 2 or more to cancel disadvantage makes it very easy for players to be unaffected by disadvantage. Powergamers are then effectively immune to rules unless you take steps to stack Disadvantage against them. You can optimize Advantage but a DM can rarely optimize for the inverse.

[Boci]

Allowing 2 or more to cancel disadvantage makes it very easy for players to be unaffected by disadvantage. Powergamers are then effectively immune to rules unless you take steps to stack Disadvantage against them. You can optimize Advantage but a DM can rarely optimize for the inverse.

In my expirience players don't regularly have advantage on attacks, so I'm unsure how they would regularly get double advantage for attacls.

[jjordan]

Thanks for the responses everyone.

[Chronos]

I like the "whichever is more, advantage or disadvantage" rule. Yes, it means that players will hunt for multiple sources of advantage. That's a feature, not a bug: Anyone going into a dangerous situation should be looking for every edge they can get. As should the enemies they're facing, which makes it balanced.

[Osuniev]

I like the "whichever is more, advantage or disadvantage" rule. Yes, it means that players will hunt for multiple sources of advantage. That's a feature, not a bug: Anyone going into a dangerous situation should be looking for every edge they can get. As should the enemies they're facing, which makes it balanced.

THIS is how I play it as well. I get that the rule make it simpler, but I hate the idea that if someone already has both Disadvantage/Advantage, then NOTHING YOU DO as any importance. Blind ? Restrained ? Surrounded ? WHO CARES, I HAVE THE HIGHER GROUND !

[Kyutaru]

THIS is how I play it as well. I get that the rule make it simpler, but I hate the idea that if someone already has both Disadvantage/Advantage, then NOTHING YOU DO as any importance. Blind ? Restrained ? Surrounded ? WHO CARES, I HAVE THE HIGHER GROUND !

Though the ease of access to advantage is done because of how easy it is to deny. The game throws advantage at you everywhere because it can't stack and counters easily. It's baked into the game balance and this upsets that balance. It's not crazy overpowered but should still be watched during your games because it greatly changes things. You don't need True Seeing to beat invisible targets if you can just stack advantage to to get the counter. What should be a silver bullet spell with an immense impact ends up being trivialized by supportive allies. Encounters that were challenging unless you had specific effects become easy for just about anyone.

[Boci]

Though the ease of access to advantage is done because of how easy it is to deny. The game throws advantage at you everywhere because it can't stack and counters easily. It's baked into the game balance and this upsets that balance. It's not crazy overpowered but should still be watched during your games because it greatly changes things. You don't need True Seeing to beat invisible targets if you can just stack advantage to to get the counter. What should be a silver bullet spell with an immense impact ends up being trivialized by supportive allies. Encounters that were challenging unless you had specific effects become easy for just about anyone.

Could you elaborate on how you imagine ahypoethical party is reliably stacking double advantage? I'm not doubting its theoretically possible under the rules, but seeing how a party need to built to achieve it will help people decide if that's a factor they need to consider for their own groups.

[KorvinStarmast]

I like the "whichever is more, advantage or disadvantage" rule. Yes, it means that players will hunt for multiple sources of advantage. That's a feature, not a bug: Anyone going into a dangerous situation should be looking for every edge they can get. As should the enemies they're facing, which makes it balanced. They wrote this edition to make it appealing to newbies as well as those of us who have been around a while. ADV/DISADV and the reduction of fiddly bits was an explicit design goal that was mostly (not completely met - I'm looking at you oversized spell book in Chapter 11!)

I thus find the desire to revert to stacking bonuses incompatible with this edition.

Now, with that said, you still have to keep track of it to see if there's a cancel out, and I was told by a player that I am the only DM they have run into who actually uses the partial cover rule consistently. (I first was exposed to it in our first ever 5e campaign, with partial and 3/4 cover being used by goblins hiding behind crates and barrels ...

So there are indeed fiddly bits remaining ... that come up with some frequency.

[Amechra]

We could just do the Shadow of the Demon Lord thing, and have advantage/disadvantage be an extra d6 that you roll and then either add or subtract from the result. If you have three sources of Advantage, say, you'd roll 3d6 and add the highest result to your d20 roll. If you have Advantage and Disadvantage, they cancel out on a one-to-one basis.