A common trend in new PbtA designs is to use an Advantage/Disadvantage mechanic (as seen in D&D 5e) over…

A common trend in new PbtA designs is to use an Advantage/Disadvantage mechanic (as seen in D&D 5e) over…

A common trend in new PbtA designs is to use an Advantage/Disadvantage mechanic (as seen in D&D 5e) over additive/subtractive modifiers. Here is what that would do to Dungeon World, mathematically speaking. [Edit: The chart represents your chance to get a 7+, 10+, or 12+. Sorry. I should have made that clear.]

Originally shared by Ray Otus

What happens when you replace +1 with an “advantage” roll in PbtA games?

Then answer is that you are about 8% more likely to hit a 7 or 10 than you were with just a +1. However, you are 1% less likely to hit 12.

[Math courtesy of AnyDice.com. “Advantage” means rolling 3d6 and taking the two best numbers.]

33 thoughts on “A common trend in new PbtA designs is to use an Advantage/Disadvantage mechanic (as seen in D&D 5e) over…”

  1. Note that if you ‘squint’ at the results, its roughly true to say the pass fail bar is 60/40 for a standard 2d6 roll, 70/30 for a +1 roll, and 80/20 for an advantage roll.

  2. Given stat modifiers I’ve never really found a problem with my players constantly failing a lot of rolls in Dungeon World as is, an 80/20 probability of success seems a little bit OTT in my opinion when you factor in stat modifiers and other abilities that increase chance of success.

  3. Yeah. I agree. The simplicity is nice but with even a +1 stat, outright failure would be too rare for my taste. OTOH it’s always good to remember that 7-9 comes with an offsetting negative detail/drawback. So full success is still harder to achieve.

  4. Ray Otus : I agree entirely, I find that–most of the time–the PCs succeed more than they fail in Dungeon World anyway, I don’t think the probability needs to be swung even more in their favour.

  5. For what it’s worth, when I use an extra die for advantage in my games, it’s not because of math—it’s because my players like rolling more dice.

  6. Jason Tocci : I’ve never really understood the urge to roll more dice, it’s never been a big things for me – but hey, if your group are enjoying it, then why not? 🙂

  7. I suppose, but why do that when failure in DW is so well rewarded? All an advantage system does is slow down the level-up rate. And fewer GM moves, which doesn’t interest me as a GM.

    EDIT 90 mins later: Yeah, okay, I suppose it symmetrizes back out if you are even-handed with disadvantages, too. I think someone just has allergies to 2d6. (Thumps on ground with cane) If it was good enough for Classic Traveller, by golly…

  8. Here’s an anydice program that compares a wide variety of odds, for PBtA roll modifiers, including –3 to +3, rolling multiple and choosing best or worst (advantage and disadvantage), rolling and then rerolling better or worse than a 3 (Yahtzee style), and the Barbarian’s 1d8. 0 is a 6–, 1 is a 7-9, 2 is a 10+ anydice.com – AnyDice

  9. Stephanie Bryant It’s a result of the fact that +1 has a higher range (to 13) even though it’s harder to initially get into that range.

  10. Bob Portnell My understanding is that people like it because advantage makes a +1 modifier feel more significant; in the base system, +1 isn’t much different from a +0.

    Past +1, the difference between advantage and modifier is pretty small, and I believe you still get a lot of 7-9 results, so it makes a smaller bonus more meaningful without sacrificing much in the way of interesting outcomes.

  11. +1 is actually a pretty big deal, despite people’s perception. I like the thought that Advantage helps cap bigger bonuses +2, +3, etc. Except it doesn’t because the stat bonuses are going to stack on top of advantage making it even more powerful.

  12. To James’s point, the appeal is that the situations where advantage and disadvantage could be used (e.g., when taking plus one forward by acting on the results of a DR, or minus one ongoing to cast spells) should be somehow different (i.e., make the mechanical effect stronger) from a simple plus or minus one. Where I have trouble is the guesswork in adjudicating exactly what stays plus/minus one, and what changes to adv/disadv. Acting on DR/SL results, fallout from 7-9 spellcasting results, and Debilities are the first that come to mind.

  13. Ah. Funny but it has never seemed problematic for me to decide when a + or -1 applies and for how long – my problem (as a GM AND a player) is just forgetting about them!

  14. Ray Otus a +1/-1 modifier has a pretty big impact on probabilities, but it often feels less influential. Why? Because you can easily tell whether it made a difference, and for normal modifier ranges (-1 through +2) a +1 modifier tips the balance only 25% of the time.

    So 3 out of 4 times, the fact that you had a +1 doesn’t really end up having mattered. And that makes it super easy to forget.

    Of course, the “crap, i got a 6… oh, wait, +1 forward because I discerned realities!” can feel pretty cool. If you remember it.

    The extra d6 for ‘vantage is less obvious clear-cut. Even if it doesn’t make a difference, you often have the feeling that it could have made a difference. And that’s pretty psychologically powerful.

  15. Jeremy Strandberg. That’s a pretty astute observation.

    Do you (or anyone) find it odd/awk to mix advantage dice and stat bonuses? That is, do most systems that use advantage for PbtA not have stat bonuses?

  16. I’ve only got a little experience with it. I grant advantage when someone uses Aid before the aided roll (and let the aider roll the advantage die). In that limited scope, it doesn’t seem very disruptive at all.

    Of course, i also have my players roll a d6 “die of fate” pretty often for stuff like “how’s the weather today?” or “do anyone here?” so the odd “straight d6” roll fits with that.

    I’m pretty sure that… someone once said that they replace +1/+2/+3 bonuses (even on the stats) with 1, 2, or 3 advantage dice (and a -1/-2 with 1 or 2 disadvantage dice).

    I’ve got no idea what that does the probabilities, but I’m pretty sure it’d affect them a lot. And I imagine it’d increase handling time for each roll.

  17. Jeremy Strandberg the anydice program I linked above has all the probabilities graphed out. What that program does not show though is that combining advantage with numeric bonuses can pretty easily push the results into never-fail territory. Rolling +2 with advantage (not really hard to acheive) gives you 5.09% chance of failure, 26.85% chance of 6-9, and 68.06% of 10+. Rolling +3 (e.g. +2 with a +1 forward) gives 10% less chance of a 10+ at 58.33%.

  18. I can see another advantage (ahem) to using advantage/disadvantage… if a player is told “you have advantage on your next roll” rather than “take +1 forward”, they can immediately pick up the extra die and have it in front of them, before it comes time for the roll. There’s thus a physical reminder of the bonus when they come to roll, which +1 forward doesn’t have.

    You can of course make physical tokens representing +1 forward using the current mechanics, but the advantage/disadvantage mechanic works with the dice you already have at the table, so it feels more elegant.

  19. I like ‘vantage, but i would only continue using it in the absence of +Stats. +’s and advantage makes for far too much success and a pretty bland story, in my opinion.

    Straight ‘vantage games or straight + games. Both are great.

  20. On that note, just thought of this. Tell me if its been done before.

    STR – advantage

    DEX – none

    CON – advantage

    WIS – disadvanatge

    INT – disadvantage

    CHA – none

  21. Robert Doe I’m going to run a PbtA-lite game for my kid. It won’t have character sheets, and I’m planning to use Advantage/Disadvantage as a catch-all for “you’re good at something or the situation favours you” (and vice versa).

  22. I think it would make for a great game. Added bonus is the extremely fast set-up. Like you said, either youre good at it or youre not.

  23. I designed a dice mechanic for DW a couple years ago with advantage instead of pluses. It went something like: roll several dice and take the highest, then roll 1d6 and add that. So it’s sorta like you have advantage on only one of your two dice.

    The stats were very close to 2d6+X but were slightly more fine grained and full success maxed out at 50%. 2d6+1 is equivalent roughly to b(2d6)+1d6 and 2d6+2 ~= b(4d6)+1d6.

    I wrote the whole thing up with graphs and stuff, I’ll see if I can dig that up later.

  24. Charles Gatz​, basicly you spread out advantage and disadvantage amongst your Stats rather than +’s. When you roll to do a thing, you take the ‘vantage into consideration and take the best or worst 2d6. No more +’s.

    It would make great one-shots. Little time needed to roll up characters. And no need to reference stat numbers. You know youre either good or not at what ever it is.

    Maybe it wouldn’t suite long games, but definitly one-shots

  25. Dawit Thepchatree yeah, the curves flatten out eventually, giving about 50% 10+ and 50% 7-9. You can go up to about b(10d6)+1d6 before that happens.

    There’s a variant b(Xd6) minus 1d6 which gives you a result of -5 up to 5, where 0-2 is a partial success. Because the negative numbers are fails and the positive are successes, you can do stuff like use the result of your roll to advance a clock or as the damage roll. If you were designing a whole new game that is.

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