Probability of Dice

Factual Questions
1

Hey,

I suck at math, and would appreciate any help.

I know that if I’m rolling two dice (six-sided dice), the probability of getting a result of 7 is 1 in 6.

If I roll the pair four times, what is the probabilty of one of those results being a 7?

In other words how do I calculate the odds that a one-in-six chance will occur, given only four chances?

Thanks,
thwartme

2

This is a simple binomial problem with n=4, p=1/6. For exactly one instance that the dice will be a 7 the probability is .3858. For 1 or more instances, it’s .4823.

3

Make that second probability .5178.

4

Thanks very much for your help.

Did I mention I suck at math? I just want to make sure I understand your answer…

If the “probability is .3858”, that means that 38.58 times out of a hundred, I can expect the result in question?

Or in other words, in four roles I’m likely to see one and only one 7 a little more than a third of the time, and two or more sevens almost half the time?

thanks,
thwartme

5

Yes and Yes.

6

The probabllity that you WON’T get a 7 in one roll is 5/6. The probability that it won’t happen four times in a row is (5/6)^4 which is 625/1296 or about 48.2% and the probability you will is 51.8%.

7

Awesome. Thanks very much.