D&D 5E Advantage / Disadvantage in 5e

[Coredump]

Sure, but isn't that kind of meaningless? You never get to choose between Advantage and a flat bonus IIRC. So you don't really have anything in 5E to compare the value of advantage to.

Its never going to happen, its just for comparison's sake. People are used to +X to hit, and most other bonuses take that form. So if you want to know how Advantage compares to Bless, or Archery.... this is how you make the comparison.

 

[KarinsDad]

Trying to recycle a good threadname here...

I just ran some numbers, and I'm seeing that advantage is MORE than an average +5 to your roll. It's +6.65.

In a game of Bounded Accuracy, that's huge.

Here's how I got the number:[sblock]
Roll two d20s, and you get 400 possible outcomes. Of those outcomes, 20 give you the same result on the die, so they're +0. Of the rest, there are no negative bonuses, because you always take the higher number. So on one end, there are 38 ways to get a +1 out of advantage. On the other, there are only 2 ways to get a +19 bonus out of advantage. Add all the bonuses from all the outcomes together, divide them by 400, and you get 6.65.[/sblock]

Let's put it this way: if you have advantage on a check, you get the proficiency bonus of a 20th level character, plus 0.65, on average.

Is my math wrong? Does advantage seem reasonable in this light?

Math flaw.

If one were to create an Excel spreadsheet with 20 rows (1-20) and 20 columns (1-20) and use the equation MAX(B$1,$A2)-MIN(B$1,$A2) (adjusted for row and column), they would get your answer.

However, this assumes that the lowest dice is always the "first dice rolled" which is the flaw.

One has to decide whether the rows or the columns are the "first dice rolled" and then remove the MAX(B$1,$A2)-MIN(B$1,$A2) and replace it by zero for those squares that are greater than or equal to the "second roll" (i.e. 15 on first roll followed by 6 on second roll is not an increase of 9, it is an increase of 0). Or alternatively, one can put an IF statement into the Excel, but I didn't bother with that.

Once that is done, the total bonus for all 400 squares (190 squares gain a bonus in 1 to 19 range, 210 gain a bonus of zero, i.e. the first roll was greater or equal to the second roll) becomes 1330. 1330 / 400 = +3.325.

This was a cool try, but mathematically flawed.

Edit: Fixed my math typo. I hate getting old and mistyping.

 

[GMMichael]

Sorry, but your math/assumptions are incorrect. There is never a "+19" benefit for advantage. . . It's never 6.65, because that's not how probability works.

Yup, my assumptions were incorrect. There actually is a +19 benefit for advantage, but my incorrect assumption led me to believe that there was a matching +19 when the dice were reversed, which there is not.

fjw70 made me ask myself: does advantage's advantage depend on sequence of rolls? Can advantage be said to grant a benefit if both rolls are made at the same time? My method assumed that the rolls did not depend on order, and that advantage was always increasing the result of the lower roll to the higher roll. Question 1: why is this incorrect?

Well, Me, this is incorrect because if I assume that the higher roll is always first, or that order doesn't matter, then there aren't 400 outcomes - there are only 210. And having (about) half of the outcomes means that about half of the 6.65 just disappeared - leaving me with 3.325.

Thanks for guiding me in the right direction, folks.

Is this the right time for me to take issue with one disadvantage negating four advantages?

 

[Sunseeker]

I like the fact that advantage/disadvantage does not stack. Either you have it, or you don't. It's a very clean and simple rule that reduces buff/debuff tracking that was prominent in previous editions, which speeds up combat and keeps the game from being hung up on "well did you add this +1/-1 to your hit?"

 

[Riley37]

Even better:

Roll 2 dice, throw away the one that failed you!

"You have failed me for the last time, Admiral..."