Timeline for Probability of 2 or more people sharing same birthday given 365 days
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| Jan 5, 2015 at 17:09 | comment | added | user2290820 | Let us continue this discussion in chat. | |
| Jan 5, 2015 at 17:05 | comment | added | user2290820 | when you say 3 factors, what do you mean? Is it (30 2) for combinations of 2s, 365P29 different ways to choose 29 ppl and 1/365^30? If so, I dont understand why 2nd term is not 365P28 instead and thats the explanation that I am looking for | |
| Jan 5, 2015 at 15:02 | history | edited | Ross Millikan | CC BY-SA 3.0 |
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| Jan 5, 2015 at 14:56 | history | edited | Ross Millikan | CC BY-SA 3.0 |
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| Jan 5, 2015 at 14:55 | comment | added | Ross Millikan | I was showing three factors to multiply and how I found them. | |
| Jan 5, 2015 at 8:59 | comment | added | user2290820 | Could you simplify further what you wrote here?: The chance that there is exactly one pair who share a birthday is (302) (the people to match)365P29(ways to choose the birthdays-the second of the pair has his chosen by the first)$/365^{30} (ways to choose the birthdays without restrictions). | |
| Jan 4, 2015 at 18:12 | comment | added | Ross Millikan | You make it very hard to understand what you are saying. It sounds like you are trying to break everybody into pairs that share a birthday, which has not been discussed before. Please write clear sentences with enough words to understand what you are thinking. | |
| Jan 4, 2015 at 18:03 | comment | added | user2290820 | Ok, starting from Range 2 upto 30, if 2 ppl share 1/365, then we've to do this for (30 2) combinations of 2 ppl.correct? and at the same time any other 2s out of the left 28 can share 1/364 of the birthdays and any of 26 can share 1/363 of bdays? What I am saying is for 1/365 there are (30 2) combinations, for 1/364 there are (28 2) combinations.. | |
| Jan 4, 2015 at 17:59 | comment | added | Ross Millikan | No, the probability a given pair share a birthday is $1/365$. The first one can have any birthday, then the second has to match that. Your next sentence makes no sense-why would you choose two out of 365 (if that is what you are doing.) | |
| Jan 4, 2015 at 17:52 | comment | added | user2290820 | still trying to understand. I understand that Prob that sm1 has a birthday is 1/365 and so for 30 ppl Prob Space => 1/365**30; Now for 2 ppl sharing 1 date that shud be (365 2). But there are (30 2) such "2 ppl" So, i.e. sum of { (365 2) for (30 2) combinations}; for 1 given date. But Range is 2-30 so we could scale this from 2 to 30. | |
| Jan 4, 2015 at 17:42 | history | answered | Ross Millikan | CC BY-SA 3.0 |