The Tuesday boy problem.
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From: master1729 on 26 May 2010 14:04 rider of giraffes wrote : > A relative of the Monty Hall problem, and currently > causing some division and argument. Originally > posed > by Gary Foshee. > > Suppose I have two children, and one of them is a > boy > born on a Tuesday. What is the probability that > both > my children are boys? > > Don't be too quick to react. Just as with Monty > Hall > some well-known and well-respected mathematicians > are > quite definite, it's just that they don't all get > the > same answer. probability = 21/40
From: Tim Little on 27 May 2010 05:31 On 2010-05-27, jmorriss(a)idirect.com <jmorriss(a)idirect.com> wrote: > I find it puzzling that some of the answers depend on the use of a > particular calendar... That because some of the assumptions depend on the use of a particular calendar... > Suppose the information was that there was a boy born on a > Tuesday...in July. Now do you use 7, or 12 to create your > fractions? Neither. In the first two of my sets of assumptions, the calendar is irrelevant. In the third, you would additionally have to assume a probability distribution for their ages and apply that to the number of Tuesdays in July in those years. If the current date was not given then I suppose it would be reasonable to assume a uniform distribution over the whole Gregorian calendar cycle. There may or may not be a 1/84 chance of being born in a Tuesday in July over that distribution. > Oh, and it was also a Tridi in Thermidor. The probabilities keeps > changing, and yet the two kids are still standing there, wondering > how likely they are... Calculations applied to models always depend upon the assumptions of the model. When a hypothetical problem omits most of the assumptions, and there are many reaonable ones, the problem is ambiguous. - Tim
From: Richard Tobin on 27 May 2010 07:14 In article <slrnhvsevc.jrj.tim(a)soprano.little-possums.net>, Tim Little <tim(a)little-possums.net> wrote: >If the current date was not given >then I suppose it would be reasonable to assume a uniform distribution >over the whole Gregorian calendar cycle. There may or may not be a >1/84 chance of being born in a Tuesday in July over that distribution. 1722/146097 -- Richard
From: jmorriss on 1 Jun 2010 16:57 On Jun 1, 3:00 pm, "John L. Barber" <jlbar...(a)lanl.gov> wrote: >>>> (Note that 13/26 = 0.481481.)<<<<<< Let's not make things more confusing than they have to be :>
From: John L. Barber on 2 Jun 2010 06:28
> > > (Note that 13/26 = 0.481481.) > > > > How much did you pay for your calculator? You > > overpaid. > > 13/26 = 0.5 according to me. > > john overpaid. > > maybe we should abolish fractions now ? :p Dammit. I edited that post to read "13/27 = 0.481481" moments after I posted it. How come no one can see the correction but me? |