math probability question for seven American nights - CORRECTION

Dimitar Nikolov · 07 Sep 2014, 20:49 · from 2014-September.txt.gz

This is the message as the crawl holds it, before anything here touched it. What the conversation shows has been through ingest: transfer encodings decoded, attachments dropped, quote markers repaired, and the archiver’s ? resolved into quotation marks and dashes. Those repairs are judgements and some of them are wrong, which is what this page is for. Email addresses are obscured here as they are everywhere else on the site, so it is before our repairs rather than byte for byte.

From: dimitar.g.nikolov at gmail.com (Dimitar Nikolov)
Date: Sun, 7 Sep 2014 16:49:47 -0400
Subject: (urth) math probability question for seven American nights -
	CORRECTION
In-Reply-To: <540CBE0D.4020705 at bindweed.com>
References: <CAF1072wp4W1u7KmwZpc=u4x7NtHz3136ZdKQbarnnVaKpxCw+w at mail.gmail.com>
	<540C5B6C.8050407 at bindweed.com> <540C5D11.5080106 at bindweed.com>
	<CADUDUCv1eeDjrscouaug528Faw6Hhv_sZOMHMbAmo4j1v9AS3A at mail.gmail.com>
	<540CBE0D.4020705 at bindweed.com>
Message-ID: <CADUDUCu+Q9ZzVLMjJF_TXxpZiN=ijQMYsS=vHMef3ixCSQ3amQ at mail.gmail.com>

You are right! This would only work for an infinite number of eggs. Sorry
for bringing my own confusion into this.

On Sun, Sep 7, 2014 at 4:20 PM, Gerry Quinn <gerry at bindweed.com> wrote:

>
> On 07/09/2014 21:06, Dimitar Nikolov wrote:
>
>> It does depend what question exactly you're asking. Indeed, the
>> probability starts at 1/6, then assuming you know that wasn't the special
>> egg, the probability for the next day is 1/5 and so on.
>>
>> You could however, ask the question, on which day is he most likely to
>> eat the egg?
>>
>> Then, you start with 1/6 for the first day once again. But the
>> probability the egg is eaten on the second day, is 1/6 times the
>> probability it wasn't eaten on the first day (=5/6), so .~.139. The
>> probability it was eaten on the third day is 1/6 times the probability it
>> wasn't eaten on either previous day, and so on. This is given by the
>> geometric distribution that you can read about on Wikipedia and results in
>> the following probabilities:
>>
>> eaten on day 1: 0.167
>> eaten on day 2: 0.139
>> eaten on day 3: 0.116
>> eaten on day 4: 0.096
>> eaten on day 5: 0.080
>> eaten on day 6: 0.067
>>
> Those probabilities don't add to 1!  You're forgetting that tghere is one
> fewer egg every day.
>
> Your figures work for a scenario in which he adds an ordinary egg every
> day, so he always has six, and chooses at random from them. Of course this
> could go on forever, as the special egg might never be chosen.  You'll find
> that the limit of the sum of probabilities goes to 1.0 after infinitely
> many days.
>
>
> - Gerry Quinn
> _______________________________________________
> Urth Mailing List
> To post, write urth at urth.net
> Subscription/information: http://www.urth.net
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.urth.net/pipermail/urth-urth.net/attachments/20140907/f7a95d1d/attachment.htm>

An unofficial mirror of a public mailing list · about & removal requests · download the archive · before the list · original archive at urth.net