Okay, I'm working on a probability issue and can't seem to get an answer that makes sense. For information, I'm trying to set up my numbers in an Excel spreadsheet.
The issue I'm trying to work is this:
I'm rolling n 8-sided dice. My goal is to find the probability of getting x or more matching dice in the set.
For example, I might have n = 13 and x = 5. I'd be trying to get 5-of-a-kind (or better) rolling 13 dice.
I've looked up a lot of probability sites and tried some of their suggested solutions, but I seem to be missing something and can't figure out what, because my probabilities end up (as an example) being less for x=3, n=10 than x=3,n=8. I've been making use of the COMBIN() function in excel, which gives the number of combinations out of a certain number of elements (for example, COMBIN(6,1) tells you there are 6 ways to choose 1 item from 6 possibilities). I know I'll be using that and/or the FACT() function, along with exponents, I just can't seem to get them in the right order to give the right results.
I'm sure this is probably a standard probability question, but the solutions I find are either non-specific (most give examples with 6-sided dice, and don't give explanations of where their numbers come from, so some of them would be different for 8-sided) or they use math notation that I can't translate to Excel functions.
Just for background, I'm basically working out some details on a game, so it's not improtant. But once I got this idea, it struck me as an interesting math problem, so now I'm desperate to figure it out. I initally thought it wouldn't take long, but I've been working on this for two days now. Any help from our resident number crunchers* would be much appreciated.
*-No offense intended: I know we have some here who don't just crunch numbers, but train them to fetch, roll over, play dead, and perform nueral surgery ;)
The issue I'm trying to work is this:
I'm rolling n 8-sided dice. My goal is to find the probability of getting x or more matching dice in the set.
For example, I might have n = 13 and x = 5. I'd be trying to get 5-of-a-kind (or better) rolling 13 dice.
I've looked up a lot of probability sites and tried some of their suggested solutions, but I seem to be missing something and can't figure out what, because my probabilities end up (as an example) being less for x=3, n=10 than x=3,n=8. I've been making use of the COMBIN() function in excel, which gives the number of combinations out of a certain number of elements (for example, COMBIN(6,1) tells you there are 6 ways to choose 1 item from 6 possibilities). I know I'll be using that and/or the FACT() function, along with exponents, I just can't seem to get them in the right order to give the right results.
I'm sure this is probably a standard probability question, but the solutions I find are either non-specific (most give examples with 6-sided dice, and don't give explanations of where their numbers come from, so some of them would be different for 8-sided) or they use math notation that I can't translate to Excel functions.
Just for background, I'm basically working out some details on a game, so it's not improtant. But once I got this idea, it struck me as an interesting math problem, so now I'm desperate to figure it out. I initally thought it wouldn't take long, but I've been working on this for two days now. Any help from our resident number crunchers* would be much appreciated.
*-No offense intended: I know we have some here who don't just crunch numbers, but train them to fetch, roll over, play dead, and perform nueral surgery ;)
via JREF Forum http://forums.randi.org/showthread.php?t=266561&goto=newpost
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