die rolling and probability [Archive] - Wizards Community

Post/Author/DateTimePost
cperkins

02-15-04, 11:01 AM
Hello all,

I have a player who almost ALWAYs misses in combat and on skill checks, rolling 1,2,3,or 5 on a d20 more times than you can imagine every game night. It's getting to the point where this player is not having fun and is sucking the life from our gaming table.

As a kindly DM, I was thinking of having this player roll [(1d10+2d6)-2] in place of 1d20.

If anyone out there knows statistics and wants to plot the %chance of rolling each # from 1-20 on 3 dice I'd be greatly appreciative.

Thanks
Seeker95

02-15-04, 11:30 AM
Without trying to calculate the exact odds, I will say your player will practically never roll a 1, 2, 3, 18, 19, or 20.

Whenever you move to more than one die, you decrease the likelihood of rolls at either end of the range, and increase the likelihood of average rolls.

I'd take my chances with a new d20 instead.
Capn Charlie

02-15-04, 11:37 AM
And a dice cup. I don't know what it is but I can't seem to roll very good at all without my trusty red yahtzee.

It may just be a placebo, but damn sure works. It is at least worth a try.
Hoarlin

02-15-04, 12:28 PM
I once played in a group with a player with the same "luck".
She never rolled higher than 5.

So we invented "reversed rolling" for her: any die roll she threw was the opposed number on the die. So 1 would be 20, 2 would be 19, 3 would be 18, etc.

Maybe an idea for your player?
Solaris

02-15-04, 07:22 PM
Try different dice, or try rolling properly; luck is not an issue here.

Here are the results you asked for.


roll ways prob
---------------
1 1 0.28%
2 3 0.83%
3 6 1.67%
4 10 2.78%
5 15 4.17%
6 21 5.83%
7 26 7.22%
8 30 8.33%
9 33 9.17%
10 35 9.72%
11 35 9.72%
12 33 9.17%
13 30 8.33%
14 26 7.22%
15 21 5.83%
16 15 4.17%
17 10 2.78%
18 6 1.67%
19 3 0.83%
20 1 0.28%
cperkins

02-15-04, 07:28 PM
Thanks a lot!

Now to run this by my group. It will probably get squashed because it all but eliminates your chances of excellent or horrendous rolls.
Serath_Aunik

02-15-04, 09:04 PM
the average is still 10.5. But remember dice aren't perfect. back in 2ed i had 2 sets of dice. one that rolled high one that rolled low, well technically i still have both sets but the low one I loan to the DM. Anyhow point being dice are weighted and if you have a really bad one go get a new one, while you're at the shop roll a few times, i'd say at least 60 and take down the numbers, it should give you a rough idea of how they roll. Remember however that it's perfectly possible that you'll get 60 20's and then it'll roll 2's for the rest of it's life so test them well before you buy.
Spongly

02-16-04, 08:59 AM
Originally posted by cperkins
Thanks a lot!

Now to run this by my group. It will probably get squashed because it all but eliminates your chances of excellent or horrendous rolls.

That's the point. One of my main problems with D&D as it stands is the high probability of a character who is really good at something messing up really badly a disproportionate amount of the time. You really should be getting average rolls more often than excellent or horrendous ones - that's why they're "average"...
airhead

02-16-04, 09:57 AM
Just superstitious - I know - but some of my dice are left-handed and must be rolled from the left hand across the table in a right direction as opposed to my right-handed dice.

Also, some dice need to be fired. I don't know if it is micro imperfections or what, but some do not roll fair. Try a new die if changing hands doesn't work.
StormKnight

02-16-04, 02:23 PM
One option to reduce luck but maintain an element of suprise would be to find or make a deck or cards numbered 1 through 20, and have players draw cards for die rolls. While this gives the same distribution of probability initially, rolls will balance out over time. For example, once you have drawn the '1' you know you won't be pulling another 1 anytime soon.
To spice it up a bit you could put in one "shuffle" and redraw card.
Of course, then your player might just always pull the '1' on her first roll, followed by the "shuffle - redraw" and the '1' again. :D
Seeker95

02-16-04, 03:24 PM
Taking StormKnight's idea a step further (a step back?) for this unlucky player...

Have him use cards instead of dice for his d20 rolls. If his luck still holds poorly, tell him to come with you to Vegas. Then bet against him in everything he decides.
channel_dunlap

02-17-04, 03:33 AM
I like the idea of using the opposite die roll. Makes sense, some odds and all that jazz. Perhaps run that by you're players too, see which they like.
jedi237

02-17-04, 10:01 AM
Watch how he rolls the dice. For a more random roll a person has to shake the dice so that it bounces around and then roll it out a distance like across the table. The cup mentioned earlier is a great idea that should accomplish this easily.