From: cescript@mtu.edu (Charles Scripter)
Subject: Re: Oh No!  NSW homicides again (Long!)
Organization: Michigan Tech University
Date: Mon, 11 Jan 1993 00:42:50 GMT

In article <LAMBERT.93Jan5225702@henna.spectrum.cs.unsw.oz.au>,
lambert@spectrum.cs.unsw.oz.au (Tim Lambert) writes:

> >>>>> On Mon, 4 Jan 1993 18:49:27 GMT, cescript@mtu.edu (Charles Scripter) said:
> > (Tim Lambert) writes:
> > Two months comes from that fact that I posted this "idea" back before
> > the end of October and your response (with much prodding) came on:
> > <LAMBERT.92Dec18025613@nankeen.spectrum.cs.unsw.oz.au> = December 18th.
> > Very nearly 2 months, Tim...
> 
> The two month delay occured between your posting of incorrect numbers
> for the deviations,

Prod, prod....  The word "Nuclear", and use of sqrt(N) didn't set off
any alarms for Lambert... 

In fact, when he read it again, his observation was "As a case in
point, we can easily see how Charles has fudged the statistics here to
prove that `a' and `b' are not significantly different.  He just made
up some errors out of thin air."  Lambert _still_ couldn't figure out
what was wrong...  "thin air", very clever Tim.  ;-)

> and between your incorrect argument that homicide
> rates were Poisson distributed.

Prod, prod...  Now I have to give Lambert the "answer"; I mention
"Poisson".  Oh!  Now Lambert can see what was wrong...  Yeehah!!... 

> Your "I got it wrong on purpose"
> claim did follow quite quickly, though.

Here Lambert wishes to imply that I actually didn't know that sqrt(N)
(for Poisson systems) is only valid for un-normalized data.  Perhaps a
fellow TPGer (he knows who he is ;-) can post some e-mail where I
discussed Lambert's poor understanding of statistics, in no uncertain
terms.  In fact, I discussed this exact post with him shortly after I
posted it... 

Don't feel bad Tim, I'm well known for doing this to students.  An
example sticks better if the student has to take a stand regarding it.
My favorite "example" is to incorrectly propagate errors for
correlated parameters, and ask them if it's correct.  ;->

> >> The rest of Charles' posting is another one of his incorrect
> >> "exercises for the student".  If anyone had trouble figuring out was
> >> wrong with it, I suggest looking in an elementary statistics book.
> 
> > The rest of my post is a refutation of Tim's proposed model, which he
> > apparently is unwilling to defend.
> 
> Since your "refutation" is as obviously wrong as your "homicide rates
> are Poisson" argument, I naturally assumed that it was another one of
> your deliberately incorrect statements.  I don't really see any need
> to defend the model against such attacks.

If one goes back and reads my post, they'll see that much of my post
is dedicated to correcting Lambert's misconceptions as to the meaning
of "Standard deviation of the sample" as opposed to "Standard
deviation of the mean". 

> >   Yes, I urge anyone who does not
> > understand Tim's "model", or my comments regarding it to refer to
> > a elementary statistics book.  Yes!! Really!! Please look it up!
> 
> I suggest looking in the index under "t-test" to find a relevant
> chapter. 

I hope everyone tried to look up "t-test" in their Stats book.  After
you fail to find it under "t-test", try looking under "confidence
levels", or something similar.  It seems that Lambert's book uses
non-standard terminology (*none* of the books I checked had a
"t-test" ;-). 

> > When examining Tim's claims, I want everyone to ask themselves (since
> > most people here are, or will be, in the professional world):  "If I
> > published a conclusion based on Tim's statistics, would it be accepted
> > to any professional journal?"
> 
> Gee, that's not too tough.  Have you seen what gets published? :-)

Yes, as a matter of fact, I have seen what gets published.  This is
why I suggested a _professional journal_; I could have added the
additional restriction that you send it to a refereed journal, but
even the unrefereed journals aren't stupid enough to run your "model".
(please note: _Time_, _Newsweek_, _Omni_, _Psychology_Today_ and other
such trash do *NOT* constitute professional journals). 

Please Tim, feel free to submit your "model" to a journal!  I suggest
the New England Journal of Medicine.  They have a well known anti-gun
slant, and maybe they'll examine your claims. 

One might wonder why I would urge Lambert to do such a thing; It's
really quite simple.  It's almost a certain fact that Lambert's
"model" will be rejected out of hand.  Lambert will be forced to
accept that his model lacks credibility.  On the other hand, there's
that one-in-a-million chance that they'll accept it, and since
Lambert's model has holes big enough to drive a truck through, this
"Journal" will be the subject of much scientific ridicule.  I don't
think I'll feel bad if NEJM loses face over this issue... ;-)

> Another question that people might ask themselves is could Charles
> pass an exam in Statistics 101?
>
> Statistics 101 - Exam

You're a riot, Tim.  Ever consider going into a career as a comedian?

Here Lambert would like to direct attention away from the points I've
addressed regarding his model, and understanding of statistics.  His
posts have relied quite heavily on obfuscation of the issue.  The
interested reader is invited to go back and see how many times Lambert
has actually discussed, or shown examples of the _method_ he used to
obtain his results. 

Now perhaps we should review some of the issues...

In response to Peter Boucher's discussion regarding crime rates in
Kennesaw following passage of the law _requiring_ ownership of
firearms, Tim makes the claim:

"If you take four successive random numbers there is one chance in
eight that they will form an ancreasing [sic] or decreasing sequence". 

I respond "Wrong Tim", pointing out this error, and post a small
program so everyone can test this for themselves (it's ~4%
probability, when restricted to real*4's, 0 =< x < 1.  One must define
the range, and granularity).  Tim responds to this with:

"To be precise: 1/24 regardless of distribution, if ties are not
possible."

Still wrong, Tim.  Here I point out it *does* depend on the
granularity of your random system (e.g. one can trivially show that
this is not true for the set: 0,1,2,3.  Only one way to form an
ascending order, and 256 possible configurations 0000-3333). 

It appears that Lambert does not know how to calculate probabilities.
And as pointed out earlier, Tim doesn't understand which Standard
Deviation is the correct measure of dispersion in a system. 

I think this establishes the fact that Lambert doesn't understand the
technical aspects of statistics, which he relies so heavily upon.  Now
let's examine some of the other aspects he has overlooked. 

I would like to know why the following factors were ignored in
Lambert's model, or why the NSW law is considered more relevant that
these other factors. 

1) Why ignore the correlation with age (16-24)?

2) Why ignore the fact that many males in that age bracket had
   recently _returned_ from fighting WWI?  [Here we notice the *huge*
   increase in homicides which appears to correspond to the return of
   the soldiers]

Let's have a look at the data (starting at zero ;-)

**************************     2.6  (1910)
***************************    2.7
************************       2.4
*********************          2.1
************************       2.4
**************************     2.6
*********************          2.1
*******************            1.9
**************                 1.4  (1918)
***************************    2.7          <----- I wonder why these 2 are
***************************    2.7  (1920)  <----- so far above 1918?...
******************             1.8  (1921) = The year the law was enacted...
****************               1.6
**********                     1.0
*********                      0.9
***********                    1.1
****************               1.6
****************               1.6
*******************            1.9
*****************              1.7
*****************              1.7  (1930)

If one were to ignore the boost in 1919, and 1920, it appears that
there is a trend for the homicide rate to slowly decrease, without
regard for the year 1921.

3) Why ignore the effects of poverty, race, socioeconomic status?

4) Was there an increase in homicides using other weapons?  Why didn't
   criminals substitute other weapons? 

5) Did the law had actually affect the number of firearms in
   circulation?

It seems that Lambert's model has some major holes in it.  One
_should_ wonder why these other factors were ignored. 

I did find an example in my stats books that seems to describe
Lambert's NSW model quite well... 

From "Statistics, A New Approach", Wallace and Roberts (1956), in the
chapter 3, "Misuses of Statistics", section 3.7, "Misuses due to
misinterpretation of association or correlation":

   "During the Italian campaign of World War II, it was found that
    there was a positive correlation between the number of propaganda
    leaflets dropped on the Germans and the amount of territory
    captured form them.  While this is consistent with the hypothesis
    that the leaflets were effective, it is also consistent with other
    hypotheses, for example, that leaflets were dropped when major
    offensives were about to begin."

Hmmmm.....  Very interesting!....  =;->

-- 
Charles Scripter   *   cescript@phy.mtu.edu
Dept of Physics, Michigan Technological University, Houghton, MI 49931
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