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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Toughest Probability Question |
| Date | 2011-12-13 16:44 -0800 |
| Organization | None to speak of |
| Message-ID | <lnaa6w6kyu.fsf@nuthaus.mib.org> (permalink) |
| References | (3 earlier) <h2rde7tob4ibdd18an0opmflg3f4gqf8pk@4ax.com> <slrnjee4qh.2irh.usenet-nospam@guild.seebs.net> <jc7kqo$egv$1@dont-email.me> <slrnjef9k1.30f0.usenet-nospam@guild.seebs.net> <jc8oom$ku5$2@dont-email.me> |
"BartC" <bc@freeuk.com> writes:
> "Seebs" <usenet-nospam@seebs.net> wrote in message
> news:slrnjef9k1.30f0.usenet-nospam@guild.seebs.net...
>> On 2011-12-13, BartC <bc@freeuk.com> wrote:
>>> and note the word "chance". With 23 people, the chance IS greater than
>>> 50%,
>>> for certain.
>
>> Since it is obviously possible to come up with a sample space *selected
>> for*
>> lack of duplicate birthdays, it is easy to have a room containing 366
>> people selected from a sample such that, no matter which 366 people you
>> pick, the chances are 0% that any have the same birthday, because if
>> they'd
>> had the same birthday as another member of the sample, they wouldn't have
>> been in the sample.
>>
>> To be *certain* of a chance is not just to do the math with common
>> assumptions.
>
> So what *is* the probability that out of a group of 23 people, at least two
> will share a birthday? Or any group of people smaller than 367? And how
> certain are you of that figure?
There is insufficient information to answer the question without
making further assumptions, in particular without knowing how the
23 people were selected.
If I were actually asked this question (say, in the course of a
job interview), I'd make any such assumptions explicit: "Assuming
that their birthdays are randomly distributed, and ignoring leap
years ...". I might also discuss alternative answers; for example,
the probability is 100% if you have two people selected to have
the same birthday, and 0% if you have 366 people selected to have
distinct birthdays.
A random uniform distribution is no more valid than any other
distribution, and there are plenty of real-world circumstances in
which a uniform distribution is highly unlikely.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Will write code for food.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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Re: Toughest Probability Question pete <pfiland@mindspring.com> - 2011-12-12 19:29 -0500
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-13 04:46 +0000
Re: Toughest Probability Question Geoff <geoff@invalid.invalid> - 2011-12-12 22:19 -0800
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-13 09:19 +0000
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-13 13:43 +0000
Re: Toughest Probability Question Keith Thompson <kst-u@mib.org> - 2011-12-13 10:27 -0800
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-13 19:52 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-13 20:06 +0000
Re: Toughest Probability Question Keith Thompson <kst-u@mib.org> - 2011-12-13 12:14 -0800
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-13 23:34 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-14 00:24 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-13 19:27 +0000
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-13 23:56 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-14 00:24 +0000
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-14 12:12 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-14 17:47 +0000
Re: Toughest Probability Question gordonb.qunma@burditt.org (Gordon Burditt) - 2011-12-15 08:22 -0600
Re: Toughest Probability Question Robert Wessel <robertwessel2@yahoo.com> - 2011-12-15 14:41 -0600
Re: Toughest Probability Question superpollo <superpollo@tznvy.pbz> - 2011-12-15 19:14 +0100
Re: Toughest Probability Question Keith Thompson <kst-u@mib.org> - 2011-12-14 13:12 -0800
Re: Toughest Probability Question Willem <willem@toad.stack.nl> - 2011-12-14 21:53 +0000
Re: Toughest Probability Question "BartC" <bc@freeuk.com> - 2011-12-14 22:35 +0000
Re: Toughest Probability Question Willem <willem@toad.stack.nl> - 2011-12-15 09:07 +0000
Re: Toughest Probability Question Geoff <geoff@invalid.invalid> - 2011-12-15 02:07 -0800
Re: Toughest Probability Question Keith Thompson <kst-u@mib.org> - 2011-12-15 12:13 -0800
Re: Toughest Probability Question Geoff <geoff@invalid.invalid> - 2011-12-15 13:03 -0800
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-15 21:36 +0000
Re: Toughest Probability Question Geoff <geoff@invalid.invalid> - 2011-12-13 16:35 -0800
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-14 01:20 +0000
Re: Toughest Probability Question Keith Thompson <kst-u@mib.org> - 2011-12-13 16:44 -0800
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-14 01:20 +0000
Re: Toughest Probability Question James Dow Allen <jdallen2000@yahoo.com> - 2011-12-15 02:33 -0800
Re: Toughest Probability Question gwowen <gwowen@gmail.com> - 2011-12-15 05:38 -0800
Re: Toughest Probability Question Thad Smith <ThadSmith@acm.org> - 2011-12-18 23:34 -0700
Re: Toughest Probability Question Bill Reid <hormelfree@gmail.com> - 2011-12-14 07:07 -0800
Re: Toughest Probability Question Kaz Kylheku <kaz@kylheku.com> - 2011-12-13 06:55 +0000
Re: Toughest Probability Question Seebs <usenet-nospam@seebs.net> - 2011-12-13 09:19 +0000
Re: Toughest Probability Question pete <pfiland@mindspring.com> - 2011-12-13 12:15 -0500
Re: Toughest Probability Question pete <pfiland@mindspring.com> - 2011-12-13 13:20 -0500
Re: Toughest Probability Question Peter Nilsson <airia@acay.com.au> - 2011-12-13 18:15 -0800
Re: Toughest Probability Question pete <pfiland@mindspring.com> - 2011-12-13 21:52 -0500
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