U of S | Mailing List Archive | alt-photo-process-l | RE: math question verrrrrry off topic

RE: math question verrrrrry off topic



Huh!!!?

After all this time, I thought I finally got it right, but it looks like
what I got is the flipped/wrong version! Since this is off topic, I won't
ask further. I will have to read some stats book again. 

Good that I don't go to casino! Whew!   :-)


Dave  

> -----Original Message-----
> From: Katharine Thayer [mailto:kthayer@pacifier.com] 
> Sent: Saturday, January 19, 2008 11:14 AM
> To: alt-photo-process-l@usask.ca
> Subject: Re: math question verrrrrry off topic
> 
> This is (one reason) why casinos make so much money, because 
> people make the mistake of thinking the probability of the 
> next throw depends somehow on how the die has fallen on the 
> last throw, but it  
> doesn't.   No matter how many times you throw the die, and no matter  
> how the die has fallen before, the probability of a 1 on the 
> next throw is still 1/6.
> 
> 
> 
> On Jan 19, 2008, at 7:57 AM, Dave S wrote:
> 
> > I must say that even in simple probability, the concept is a little 
> > hard to grasp for me. I can do the math, but to FEEL it is 
> different.
> >
> > Say I am throwing a dice now. The chance of getting a 1 is 1/6.  
> > Let's say I
> > did get a 1. Now I am throwing again. I pick up the same 
> dice and make 
> > the same random throw. On one hand I think everything is 
> the same, so 
> > the probability of getting 1 should still be 1/6. On the 
> other hand, 
> > of course, chances of getting two 1's in a row is lesser, so the 
> > probability is now 1/36.
> >
> > If this is an exam in the statistics class, I can do the math and 
> > pass, but up to this day, my mind would still flip one way 
> or another 
> > because both are making some sense to me. Isn't this weird?
> >
> >
> > Dave
> >
> >
> >> -----Original Message-----
> >> From: Katharine Thayer [mailto:kthayer@pacifier.com]
> >> Sent: Saturday, January 19, 2008 9:52 AM
> >> To: alt-photo-process-l@usask.ca
> >> Subject: Re: math question verrrrrry off topic
> >>
> >> Okay, look.
> >>
> >> If this were a simple probability experiment, let's say there were 
> >> 600 objects in a big jar, all exactly the same size and shape and 
> >> differing only in color:  450 red ones (for
> >> not-accepted) and 150 green ones (for "accepted")  all mixed up 
> >> really well, and the question was, "if some people from College X 
> >> reached into the jar blindfolded and three of them pulled 
> out green 
> >> objects, what would the probability of that result be, would it be 
> >> 1/4x1/4x1/4?"  then the answer would be  "only if just 
> three people 
> >> from College X reached into the jar.  If more than three 
> people from 
> >> college x reached into the jar, let's say five people from 
> college x 
> >> reached into the jar, then the probability of three of those five 
> >> people pulling out a green marble would be 1/4 x 1/4 x 1/4 x
> >> 3/4 x 3/4."
> >>
> >> But of course this isn't anything like that.   In this 
> case, the 600
> >> objects in the jar are made by the people who are being 
> selected, and 
> >> the objects are all different, all different sizes and shapes and
> >> colors, and made of different materials.   People might contribute
> >> different numbers of objects (though it's never been clear to me 
> >> whether that's the case or not) in which case the objects 
> made by the 
> >> same person presumably aren't as different from each other as the 
> >> objects made by different people.  And the selection is 
> made not by 
> >> the people themselves reaching into the jar blindfolded, but by a 
> >> third party, a judge, who also doesn't reach into the jar 
> blindfolded 
> >> and pull out objects randomly to make a selection, but 
> pours them all 
> >> out on in a big tray and looks at all 600 of them closely before
> >> deciding which ones he/she wants to include.   This 
> particular judge
> >> might be drawn to metal objects, or even especially to 
> platinum over 
> >> silver, or maybe he or she particularly dislikes street scenes and 
> >> prefers pictures of old mills, or is looking for a certain 
> level of 
> >> craftsmanship in the work, or maybe the criterion is 
> something even 
> >> more difficult to articulate, whether the judge "likes" 
> something or 
> >> not.
> >> Whatever the criteria, by the end of the day, the objects are 
> >> separated into two piles, "accepted" and "not accepted," and there 
> >> are 150 objects in the first pile and 450 in the second pile.
> >>
> >> I hope it should be clear to everyone at this point how different 
> >> this is from the problem above, and why you can't treat this as a 
> >> problem of simple probability  and say that the probability of any 
> >> entry being accepted is the same as the probability of any other 
> >> entry being accepted, and that this equal probability for 
> each entry 
> >> is 1/4, since 1/4 of all the entries were accepted.  It's just not 
> >> that kind of problem, and it doesn't work to treat it that way.
> >> Thank you.
> >> Katharine
> >>
> >>
> >>
> >>
> >> On Jan 18, 2008, at 6:49 PM, Katharine Thayer wrote:
> >>
> >>
> >>> :--)
> >>>
> >>>
> >>> On Jan 18, 2008, at 6:23 PM, Diana Bloomfield wrote:
> >>>
> >>>
> >>>
> >>>> Hey Katharine,
> >>>>
> >>>> I don't know-- maybe.  I honestly didn't read the other
> >>>>
> >> answers.  :)
> >>
> >>>>
> >>>>
> >>>> On Jan 18, 2008, at 8:43 PM, Katharine Thayer wrote:
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> Hmm, I thought that's what we all already have said, isn't it?
> >>>>> That that theoretical probability (1/4x1/4x1/4) would
> >>>>>
> >> hold only if
> >>
> >>>>> assumptions were met,  and since assumptions are
> >>>>>
> >> obviously not met
> >>
> >>>>> (for example, judging is not a random lottery of course
> >>>>>
> >> but is done
> >>
> >>>>> on the basis of criteria, arbitrary or otherwise but
> >>>>>
> >> certainly not
> >>
> >>>>> random).  Also, no one has said whether the 600 entries are 600 
> >>>>> works or 600 people; I was assuming that they are 600 works 
> >>>>> representing fewer than 600 people, in other words people could 
> >>>>> submit more than one work, in which case, as I said, the
> >>>>>
> >> number of
> >>
> >>>>> works submitted per person would also have to be 
> figured into the 
> >>>>> equation somehow.  Besides, if one person submits ten 
> pieces and 
> >>>>> another person submits one, the ten pieces by the one person 
> >>>>> couldn't be considered independent entries in the same 
> way one of 
> >>>>> those ten could be considered independent of the one from
> >>>>>
> >> the other
> >>
> >>>>> person, and independence is also an assumption that must
> >>>>>
> >> be met in
> >>
> >>>>> order to consider the probability of acceptance to be the
> >>>>>
> >> same for
> >>
> >>>>> all entries.
> >>>>> Katharine
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Jan 18, 2008, at 4:25 PM, Diana Bloomfield wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>> Okay, Chris.  Here is it-- straight from my resident
> >>>>>>
> >> statistician
> >>
> >>>>>> here:
> >>>>>>
> >>>>>> If they were the only 3 people from that institution who
> >>>>>>
> >> applied,
> >>
> >>>>>> AND if judging was completely random, then the
> >>>>>>
> >> probability of this
> >>
> >>>>>> is roughly 1 in 64 (key word: roughly).  If more than
> >>>>>>
> >> that applied
> >>
> >>>>>> from this same institution, and only 3 got in, then the
> >>>>>>
> >> calculation
> >>
> >>>>>> will be more complex.
> >>>>>>
> >>>>>> Hope that helps. :)
> >>>>>> On Jan 17, 2008, at 12:00 PM, Christina Z. Anderson wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>> Where else but this list can I ask these weird 
> questions about 
> >>>>>>> chemistry and math and computers and alt???
> >>>>>>>
> >>>>>>> OK for you math people (Yves?):  If there is a show and 600 
> >>>>>>> entries, and 150 are accepted, there is a 1 in 4 chance of 
> >>>>>>> acceptance.  If 3 people from the same institution 
> are accepted 
> >>>>>>> what percent chance is that--is it 1/4 x 1/4 x 1/4 or a 1.5% 
> >>>>>>> chance or is it a more complex formula?
> >>>>>>>
> >>>>>>> Forgive the off topic request but it does relate to
> >>>>>>>
> >> photo as 3 of
> >>
> >>>>>>> our program got into a photo show and I want to be able to 
> >>>>>>> mathematically brag about it to the dept. head/dean.
> >>>>>>> Chris
> >>>>>>>
> >>>>>>> Christina Z. Anderson
> >>>>>>> Assistant Professor
> >>>>>>> Photo Option Coordinator
> >>>>>>> Montana State University
> >>>>>>> CZAphotography.com
> >>>>>>> _______________
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>>
> >>
> >>
> >>
> >>
> >
> >
> >
> 
> 
>