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

John Knight jwknight at polbox.com
Tue Aug 20 23:03:09 EST 2002

```"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?
> >
>
> 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)
>
> 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?

John Knight

```