# brain sizes: Einstein's and women's--jet

Parse Tree parsetree at hotmail.com
Mon Jul 22 18:58:44 EST 2002

```"John Knight" <johnknight at usa.com> wrote in message
news:hV%_8.15461\$Fq6.1564776 at news2.west.cox.net...
>
> "Bob LeChevalier" <lojbab at lojban.org> wrote in message
> news:t0jnjusa3s0ndrh1cnq9jtq4im8rgmfasb at 4ax.com...
> > "John Knight" <johnknight at usa.com> wrote:
> > >> What part of "less than zero percent of American girls got the
correct
> > >> answer" did you NOT intend, and how does it make any sense, so matter
> how
> > >> much you "adjust it for guesses"?
> > >>
> > >
> > >Let's try to break this down into real simple pieces so American 12th
> > >girls may be able understand it.
> > >
> > >If you have a red straw, a green straw, a blue straw, and a white
straw,
> and
> > >you ask a student to pick one at random, then if they pick it randomly,
> the
> > >probability of picking the red one is 0.25, and the green one is 0.25,
> and
> > >the blue one is 0.25, and the White one is 0.25.
> > >
> > >If you put all four straws back in your hand and ask them to pick them
> > >randomly again, the probability is the same thing again.  If you do it
> two
> > >more times, then the overall probability of picking each color is 1.0:
a
> > >red one = 1.0, a green on = 1.0, a blue one = 1.0, and a white one =
1.0.
> >
> > Let's break this down in real simple pieces so a 1st grader could
> understand.
> >
> > NO! YOU ARE WRONG!  BAD JOHNNY! Go sit in the corner with the pointy
hat!
> >
> > You don't know what you are talking about.  You don't know how to
> calculate
> > probability.  One is tempted to think that you don't know what
probability
> > means.
> >
> > Lest you need an example, the probability when flipping a coin randomly
is
> .5
> > for heads and .5 for tails.  It is NOT the case that if you flip a coin
> twice
> > that the probability is 1.0 that you will get heads once.  If you doubt
> this,
> > then try flipping coins twice several times.  If the probability is
indeed
> > 1.0 that you will get heads once, then that means that in EACH pair of
> flips,
> > EXACTLY one of the two flips will be heads.
> >
> > This will NOT happen, unless you have truly exceptional luck.  Sometimes
> you
> > will get two tails and NO heads, sometimes you will get TWO heads and no
> > tails, and sometimes indeed you will get 1 head.  Roughly half the time
in
> > fact.
> >
> > >This doesn't mean that this is exactly what you'll get on the first
> set--but
> > >if you were to do this a million times, you would have 250,000 red,
> 250,000
> > >green, 250,000 blue, and 250,000 white, IF the student actually picked
> the
> > >straws at random.
> >
> > If the probability was 1.0 for each color in 4 drawings, then that means
> that
> > EVERY time, without fail, you drew 4 straws at random, you would get
> exactly
> > one of each color.  That is what a probability of 1.0 means.
> >
> > My best guess it that you are confusing "probability" with some
perversion
> of
> > the concept called "expected value".  But you'd have to learn the
> difference
> > before it would be worthwhile exploring whether that was what you were
> > talking about.  I don't propose to teach you basic probability theory.
Go
> > back to school or read a book (or even a good internet site if you don't
> know
> > what a book is).
> >
> > >What bias do American 12th grade girls have against so many correct
> >
> > What bias do you have against learning something about what you are
> talking
> > about?  Like basic probability theory.  Like maybe the answer to H04 and
> how
> > those girls (and boys) were supposed to figure it out.  Right now you
are
> > demonstrably dumber than a 12th grade girl.
> >
> > lojbab
>
>
> Now we know what's wrong with "liberals", don't we?  You "think" you're so
> smart, but you're stupider than door knobs.  You are DEAD WRONG, and maybe
> now you know why--you don't have a clue about what "probability" even
means.
>
> So let's make it REAL simple. Let's define a simple statement of the
> problem.
>
> If you have 100,000 students *randomly guessing* at one multiple choice
> question which has four possible answers (A., B., C., and D.), one of
which
> must be selected, then there is only ONE possible outcome:
>
> A. gets selected 25,000 times.
>
> B. gets selected 25,000 times.
>
> C. gets selected 25,000 times.
>
> D. gets selected 25,000 times.
>
> Unless the correct answers are not distributed evenly across A., B., C.
and
> D. (i.e., unless the test designers didn't assign the correct answers
> randomly), then there is NO other possible outcome (except for an initial
> minor variation from these figures which would eventually even out over
> time).

You're pretty ill informed.  Firstly, when guessing, the correct answer has
no bearing on what is guessed.  Thus if the answer is really A, that has no
effect on me guessing (since by guessing, we assume that they do not know

Additionally, while the expected value for A is 25000, that doesn't mean
that A will be picked 25000.

> If the correct answer is B., and this answer is selected by 25,000 girls,
> then you have zero evidence that they properly applied the theories to
> resolving the problem.  If they selected this answer 25,750 times, you
still
> have no evidence that they understood the principles, or could apply them,
> because such a score would be lower than the 3% standard error.  If they
> selected this answer 30,000 times, you are just barely higher than the
> combination of the 25% multiple choice guesses and the 3% standard error,
> which starts to make the score meaningful.

What 3% standard error?  There isn't some percentage that denotes a standard
error.

There exists a probability that even while guessing, every single person
picks A.  The probability is slim, but it still exists.

```