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View Full Version : Success Probability in World of Darkness



Whammydill
2010-03-12, 01:21 PM
It seems pretty hard to fail at something in nWoD. With most things only requiring one success to work, with a set difficulty number. Anything 8 or more is a success. Thats 30% chance of success on a single dice. Even if reduced to a chance dice you have a 10% chance of success, by rolling a 10 on said dice. Compred to other game systems it seems pretty hard to fail at anything with even a small dice pool in nWoD. I'm trying to get one of our StoryTeller's to realize that he needs to incorporate more (sensible) penalty dice to bring about the challenge that should be present in the system.

Now, I suck at math and I'm sure this is LoLeasy math but it's beyond me. I was wondering how one would calculate the odds of one success given a number of 10 sided dice, expressed as a percent chance of success.

Say:

1d10 = 30%
2d10 = ?
..etc.

Any insight on this FailAtMathITP post?

pffh
2010-03-12, 01:29 PM
I always find it easier to calculate the chance of failure in cases like this:

1d10 = 7/10 = 70%
2d10 = 7/10 * 7/10 = 49%
3d10 = 7/10 * 7/10 * 7/10 = 34.3%
4d10 = 7/10 * 7/10 * 7/10 * 7/10 = 24.01%
etc

And finally just for fun with 10d10 you have 2.8248% chance of failure.

senrath
2010-03-12, 01:45 PM
And yet, there will be times when the players have a 15 dice pool and not get a single success. Repeatedly.

valadil
2010-03-12, 02:04 PM
How do opposed rolls work? Maybe that's where the challenge is supposed to be?

hiryuu
2010-03-12, 02:08 PM
And yet, there will be times when the players have a 15 dice pool and not get a single success. Repeatedly.

And sometimes there are people who've never seen that happen in five years of playing. Probabilities are funny that way.

Kylarra
2010-03-12, 02:10 PM
How do opposed rolls work? Maybe that's where the challenge is supposed to be?Opposed rolls are your successes vs their successes.

Selrahc
2010-03-12, 02:23 PM
The possibility of success is actually exactly 1/3 due to ten again. Although that doesn't really affect the odds of getting exactly one success. Makes it easy to work out the average number of successes for a given dice pool though.


How do opposed rolls work? Maybe that's where the challenge is supposed to be?

There are various different types of rolls. Most common are just a roll of skill to try and get one success, with penalties based on difficulty. Then there are extended rolls to try and get to a target number of successes over a period of time. Contested rolls are also common and are rolled against an opponent with the side with most successes winning. Combat is done with each success subtracting one point of the opponents health, so more than one will be needed to seriously injure or kill an opponent.

Project_Mayhem
2010-03-12, 02:35 PM
It's far better than the dice pools in OWoD, where you were more likely to botch the better you were at something.

And opposed rolls are difficult. Last Mage session, I was trying to remove my teammate's sympathetic connection to the BBEG with space magic (basically removing the chance of him casting magic on him from a distance). My dicepool was 9 - 4 Space, 3 Gnosis, 2 High speech, against a composure+gnosis roll that could have been from 4-8, but was probably about 6-7 (We keep our stats secret). I swear, it took me multiple goes to get even 1 success. In the end I just got him drunk and played lloud grime music at him to give him a penalty.