Probability of modified 2d6 rolls.
Hey DW people. I’m not so great at statistical math… Can anyone help me figure out what the probabilities are of rolling any given number on a modified 2d6 roll? I’ve seen the straight 2d6 charts before, but how does that look with the modifiers?
You can make these charts easily on anydice.com
Harald Wagener is on the money
anydice is invaluable… love that thing.
I’ve no idea how to read the charts, but I guess I bookmarked this a while ago 😛 http://fsckme.zehta.me/2014/03/dungeon-world-dice-probabilities.html
I don’t know if this is relevant, but when designing custom moves, change the granularity of the moves themselves instead of the dice probabilities. It prevents a lot of confusion.
Totally, Tim Jensen, I was just personally curious to know how it looks from an actual probability standpoint.
The probabilities of each roll stays the same but the value associated with each probability slides up and down by the modifier. http://anydice.com/program/4725
Right, that’s what one of those colourful graphs
that Em0srawk posted says. +3 is a pretty huge advantage… Something to keep in mind I guess…
I put a bunch of these on my blog sometime ago:
http://redmoosegames.blogspot.com/2014/10/probabilities-of-2d6-with-common-pbta.html
http://redmoosegames.blogspot.com/2014/10/couple-more-aw-probability-graphs.html
The following puts some context around the probabilities:
+5 is superman territory: the character cannot fail, and only 1/6 rolls will be 7-9; everything else will be 10+
+4 is true mastery: 10+ results will dominate (72%; vs 25% for 7-9 results) and the character will almost never fail (only 1/36 chance)
+3 is probably the sweet spot for something the character is expert at: successful a lot of the time, 10+ approx 60% of the time, with only the occasional fail (1/12 chance of a fail)
+2 is good for something the character has a decent competence at: successful most of the time; 40% of rolls will be 10+; but expect a fail every few rolls (~50% chance every 3-4 rolls)
+1 means the character will usually do ok, but not great: rolls are mostly successful with 27% getting to 10+, however fails are common (~50% chance every 2 rolls)
+0 is risky: while the character has ~60% chance of success, they have only 1/6 chance of getting a 10+, and fails will be frequent (every two or three rolls).
-1 is asking for trouble: the character will fail more often than not, and has only a 1/12 chance of rolling a 10+
-2 is getting desperate: the character will fail 72% of the time, and has only 1/36 chance of getting a 10+
-3 is last ditch rolling: the character has an 83% chance of failing and even the best success will still only produce a 7-9.
It’s worth remembering, too, that the more characters have to roll, the more likely they are to fail.
For example: while a single +1 roll has only 28% chance of failing, making the character roll twice to achieve the result they want increases their chance of rolling a fail to almost 50%.