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Hello, I'm doing my math fair on dice probably in Warhammer 40k and i need a formula. So here is the question:

If i'm rolling one die and i need a 3+ what would the formula be for that occurring.
This formula must work for 2+, 3+, 4+, 5+ and 6+.

Break it down by percentages. A D6 will roll a 6 approximately 16% of the time, a 5 or a 6 approximately 33%, and so on.

Probability 101:

Probability = {number of desired outcomes} / {number of total outcomes}

Therefore a 3+ is 4/6.

PS: this is why you use google before posting, since this is incredibly basic math that you could have learned in the time it took you to press the "post" button.

Chances of rolling required number = (7-x) / 6

x being the number you need (i.e 3 for 3+, 4 for 4+ etc.)

It depends on the situation, Dice have worse rolls when you really need them.

I tried Google but couldn't find anything that i needed.


Automatically Appended Next Post:
I also already knew everything everybody else said other than glorioski.

 necronuser wrote:
I tried Google but couldn't find anything that i needed.

Apparently not very hard, because the first google result for "dice probability" gives you exactly the answer you're looking for in very simple terms.

http://lmgtfy.com/?q=dice+probability

Edited by Manchu.

 Peregrine wrote:
Probability 101:

Probability = {number of desired outcomes} / {number of total outcomes}

Therefore a 3+ is 4/6.

PS: this is why you use google before posting, since this is incredibly basic math that you could have learned in the time it took you to press the "post" button.

This is your answer.

It is, of course, slightly abstracted as it doesn't take into account things like the rotation of the dice, the effect of the shape of the dice as they roll, the playing surface, etc. For instance, I think dice with rounded shoulders perform significantly worse than ones with rigid shoulders? Something to do with momentum and points of balance. I think the '1' side wants to be on the bottom, but with rounded edges it's more likely to roll one more time, while with square edges more momentum is required for each roll, so the '1' is more likely to stay on the bottom. There was a study on it somewhere, but I can't be bothered finding the link. It's also the reason casinos use square edged dice.

 Glorioski wrote:

 Peregrine wrote:
PS: this is why you use google before posting, since this is incredibly basic math that you could have learned in the time it took you to press the "post" button.

 Peregrine wrote:

 necronuser wrote:
I tried Google but couldn't find anything that i needed.

Apparently not very hard, because the first google result for "dice probability" gives you exactly the answer you're looking for in very simple terms.

http://lmgtfy.com/?q=dice+probability

You do know it's perfectly acceptable not to be a condescending dick on this site, right?

It's perfectly acceptable to be condescending too.

It's also perfectly acceptable to google things before you post.

When did perfect acceptability dakka, guys?

I'm going to slightly hijack this thread, just a tad.

How do you do cumulative percentage? Tried looking it up before but couldn't quite figure it out.

Like, what are the odds of rolling 6 with 5 dice?

It's 1/6 with one. But going ahead is where I completely blank out from my lessons back in highschool

 Necroshea wrote:
Like, what are the odds of rolling 6 with 5 dice?

To calculate "at least one of X in Y tries" the easiest way is to calculate the probability of rolling not-X in all Y tries, and then take the inverse of it. So, for your question, it would be 1 - {(5/6)^5}.

If you want more than one success you need to use binomial probability, which is more complicated and best done with a calculator.

 Peregrine wrote:

 Necroshea wrote:
Like, what are the odds of rolling 6 with 5 dice?

To calculate "at least one of X in Y tries" the easiest way is to calculate the probability of rolling not-X in all Y tries, and then take the inverse of it. So, for your question, it would be 1 - {(5/6)^5}.

If you want more than one success you need to use binomial probability, which is more complicated and best done with a calculator.

I see. Thank you.

 cox.dan2 wrote:
It depends on the situation, Dice have worse rolls when you really need them.

Well of course, this!

I am glad the OP asked this as I think more people need to understand the statistics behind dice rolling. I get so sick of hearing about unlucky dice rolling.

I don't believe in luck, I believe in math. Statistically you have a 1/6 chance of rolling any number assuming your dice are balanced. There is no luck only statistics.

We wrote:
I am glad the OP asked this as I think more people need to understand the statistics behind dice rolling. I get so sick of hearing about unlucky dice rolling.

I don't believe in luck, I believe in math. Statistically you have a 1/6 chance of rolling any number assuming your dice are balanced. There is no luck only statistics.

What's really bad is I have a friend who almost seems to outright refuse to acknowledge the behind the scenes math.

I remember discussing the tau vespid. Told him how it was a bad unit and brought forth some mathhammer to prove the point (in a non rude way I might add), and he just threw the math evidence in my face and ever since then flat out says he doesn't care about that line of thinking.

Some people.

You forgot to factor in the Favor/Disfavor of the Dice God(s), which is a huge variable! :O Did you do anything to displease them, say your prayers, make a sacrificial offering? What type of terrain are you rolling on? The math behind the dice roll is truly staggering with all things considered!

Anoint your dice in the blood of martyrs and butcherd children and you will be rolling the numbers when you need them, worked very well for me

necronuser wrote:I tried Google but couldn't find anything that i needed.

Not very well.

When I type in "1D6 statistics" I get this as the third result, and when I do 2D6 statistics, I get this as literally the first result.

 Necroshea wrote:
I'm going to slightly hijack this thread, just a tad.

How do you do cumulative percentage? Tried looking it up before but couldn't quite figure it out.

Like, what are the odds of rolling 6 with 5 dice?

It's 1/6 with one. But going ahead is where I completely blank out from my lessons back in highschool

A good rule of thumb is that if your end result is more than 1, you propably did something wrong. Assuming you didn't multibly the odds with something (ie 5*1/2)

Well, Probability 101 is easy.
If you want to roll 3+, then the outcomes should be 3,4,5, or 6.
So in 4 of 6 cases you get the desired outcome, giving you the relative frequency 4/6 = 0.66.

In general, all probabilities above 50% are good. The rest should be considered as bad.