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Message from discussion Linear regression
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Reef Fish  
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 More options Jun 1 2006, 7:44 pm
Newsgroups: sci.stat.math
From: "Reef Fish" <Large_Nassau_Grou...@Yahoo.com>
Date: 1 Jun 2006 16:44:54 -0700
Local: Thurs, Jun 1 2006 7:44 pm
Subject: Re: Linear regression
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Reef Fish wrote:
> Richard Ulrich wrote:
> > On 31 May 2006 09:58:58 -0700, "Jens" <jens.sto...@gmail.com> wrote:

> > > Thanks Bob for your prompt answer.

> > [snip, some]

> > Bob >
> > > <skip>
> > > > By "couplings" I think you mean either statistical or deterministic
> > > > relations some pairs of X's.  Short answer, as long as the X's are linearly
> > > > independent, there's nothing to worry about.
> > Jens >
> > > By couplings I mean some unknown relations between the columns. Unknown
> > > in the sence that no-one have investigated such relations properly, but
> > > based on "intelligent" guess some relations surely exists.

> > Does that matter?  Maybe, maybe not.

> > Reef Fish Bob belongs to a "black-box" school of regression --
> > the statistician has no knowledge of control of any of the
> > many variables going into his equation, and no care for what
> > it may "mean".   [And, in his ignorance, Bob is exceeding proud
> > that his way is the only right way.]

> It is too much to expect Richard Ulrich to be on good behavior
> for long.   The monkey on his back is on his back again.

> More later.   Have a plane to catch.

Now I can give a better diagnosis of Ulrich's gratuituous, but very
familiar attack, based on HIS OWN lack of understanding of the
subject to which I gave jens my advice.

It should be clear from the post to which I replied jens that he was
asking the most basic questions about linear regression model, not
having ever read any book of article on the subject, from his
description of

> So my model should be Xb=y+e and e=Xb-y should be "close to" iid N(0,
> sigma^2).

which I corrected him to,

RF>  It's  Y = Xb + e,  where e is nearly iid N(0, sigma^2).

responded to his simple questions simply, and then adviced that reading
a book such as Neter, Kutner, Wasserman, Nachsheim is textbook
should be of great help to him.

There was NO indication whatsoever that jens was speaking of a
designed experiment, or a controlled observational study;  or that
jens is even familiar with the basic notions of a linear model!
That's
when Richard Ulrich thought he found the opening to insert his
favorite salemanship of Quackery and Snake Oil,

> > Reef Fish Bob belongs to a "black-box" school of regression --
> > the statistician has no knowledge of control of any of the
> > many variables going into his equation

After his by now familiar style of gratuitous attack,  Ulrich didn't
have much go on his own other than:

RU>  What is your N?  ... your number of predictors, your expected
RU>  R-squared?   Do you have a choice of what variables to use,
RU>  or what functional forms of them?  With Large-N and large-P
RU>  and no choice in the variables, you should follow Bob's
RU>  lead -- run the regression and study the diagnostics....

Apart from MISQUOTING my advice to jens, Richard Ulrich had
nothing of his own to offer.

Now that jens has given him the description of his problem, more
than 12 hours ago, and Richard Ulrich had followed up on another
post about an hour or so ago (so he is around), Ulrich has NOTHING
to offer jens, after he wasted no time (May 31, 4:30 pm) attacking
my post of May 31, 2:05 pm to jens which jens thanked me for
my suggestion on June 1, 6:39 am,

jens>  I was able to locate Neter, Wasserman & Kutner book on
jens>  "Applied Linear Statistical Models", third ed, 1990. So that
jens>   will keep me busy for a while.

and gave Richard Ulrich a description of his problem on June 1,
6:56 am, as Ulrich had asked.

The supreme irony of this particular situation is that jens KNOWS
he is unfamiliar with linear regression models, and had followed my
advice to read up on it.

Richard Ulrich, on the other hand, had made ALL THE ERRORS
that are POSSIBLE, for anyone who had taken a course using
the material in Neter el al -- as evidenced by what's in the archives
-- Richard Ulrich knew even LESS than jens about LINEAR MODELS,
and Ulrich had no idea what the regression assumption are, about
the X's, what the error assumption are, and when to test them, and
various misinformation and errors made by Ulrich about the sign,
and the meaning of the multiple regression coefficients ...

felt obliged to rise to this occasion, in the guise to help jens, to
proclaim his completely unwarranted attack, based on what I had
adviced jens!!

> > Reef Fish Bob belongs to a "black-box" school of regression --
> > the statistician has no knowledge of control of any of the
> > many variables going into his equation, and no care for what
> > it may "mean".   [And, in his ignorance, Bob is exceeding proud
> > that his way is the only right way.]

Richard Ulrich, you are hopeless and beyond redemption.

The one line sums it all up, given THIS post in which I gave my
substantiated REASONS why.

-- Bob.


 
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