# brain sizes: Einstein's and women's: Mat

Parse Tree parsetree at hotmail.com
Wed Aug 21 00:31:20 EST 2002

```"John Knight" <jwknight at polbox.com> wrote in message
news:1iE89.56385\$eb.4167626 at news2.west.cox.net...
> "Bob LeChevalier" <lojbab at lojban.org> wrote in message
> news:j1r5mu07emjtsagjd4c7sigpje9c5id87l at 4ax.com...
> > "John Knight" <jwknight at polbox.com> wrote:
> > >"mat" <mats_trash at hotmail.com> wrote in message
> > >> mats_trash at hotmail.com (mat) wrote in message
> > >> > No it won't you fool.  Answer we this, and don't conveniently avoid
> it
> > >> > like the other difficult parts of my last post:
> > >> >
> > >> > If a coin is flipped twice am I certain to get one head and one
tail
> > >> > (as would be the case according to your logic.
> > >> >
> > >> > If I flip a coin three times, what is the probability of getting at
> > >> > least one head?
> > >> >
> > >> > Just answer those questions and we know where we stand.
Furthermore,
> > >> > if you don't answer you will confirm your inability to comprehend
> > >> > basic mathematics.
> > >>
> > >> Surely not that hard?
> > >
> > >Not only was your question answered a long time ago,
> >
> > Nope.
> >
> > >The probability of getting one head on the first flip is 0.5.  The
> > >probability of getting two heads in a row are 0.5 x 0.5, or 0.25.  Of
> > >getting three in a row is 0.125, etc.
> >
> > That is not the right question.  .125 is the chance of getting THREE
> > heads in a row on three coin tosses.  The poster asked you the
> > probability of getting AT LEAST ONE head in three coin tosses.  You
> > don't know the answer, do you?
> >
> > The correct answer is .875.  Now given the answer, can you tell us WHY
> > that is the correct answer?  I've done half the problem for you, and
> > I'll bet you STILL can't solve it.
>
> This is TOO funny.  Using binomial probability to determine the
probability
> of thousands of students getting ONE correct answer out of 4 multiple
> choices is a far different probability problem than using binomial
> probability to determine "AT LEAST ONE head in three coin tosses".
>
> >
> > >But that's an entirely different question than the probability of
> thousands
> > >of students (randomly guessing on a four part multiple choice question)
> > >getting the correct answer.
> >
> > You guessed wrong on his question.  The probability that you would do
> > so was nearly 1.000, but that has little to do with random selection.
> >
>
> Nobody "guessed wrong on *his* question".  The question is irrelevant to
the
> original POINT.
>
> And the following suggests that *his* tactic worked--you're both spinning
> around in left field, once again.
>
> > >No matter how you slice it, if the guesses are truly random, the larger
> the
> > >sample size, the closer you'll be to 25%.
> >
> > But they aren't random any more than your wrong answer to his problem
> > was random.  You misunderstood the question.  This makes you no better
> > and probably worse than most of those female students you like to
> > insult.
> >
>
> Nobody misunderstood *his* question.  Nobody denies you can use binomial
> probability to calculate the answer to his question, and nobody denies
that
> you (amazingly enough) actually calculated it correctly.
>
> But *he* is supposed to be answering a *completely* different question.
> This has utterly nothing to do with that question.  This distraction from
> the original question accomplishes nothing.  The question is, ASSUMING
> random guesses by thousands of students, what is the distribution of the
> responses going to be on a four part multiple choice question.  Since
nobody
> seems to *want to* [read: is able to] answer that question, here is the
>
> 25% plus or minus 2% will select A)
>
> 25% plus or minus 2% will select B)
>
> 25% plus or minus 2% will select C)
>
> 25% plus or minus 2% will select D)
>
> No matter how much you confuse yourself with all these other irrelevant
> points, there's no other possible distribution of the responses if they
were
> completely random.
>
> Right?

You're assuming a uniform distribution.  Also, it's probably 25% not WILL
BE.  There isn't any certainty.

Also, humans cannot guess randomly.

```