Re: M6 problem survey

[ABreull@aol.com]

In einer eMail vom 05.09.1997  12:11:41, schreiben Sie:

>let me say as I said before (and several other people have
>said) that Fernando's statistical methods are unsound.  They are bad, bad,
>bad.  

- ------- snipping a lot of inelligent arguments for brevity

> Second, he has invited his survey participants to
>select themselves, based on how interested they are in his survey.  This
>will produce biased results.

- -------- snap

You are true - maybe. Depends on the standpoint. 

First, as I pointed out before, it depends on the character and meaning of
the observed event. You would not have wanted to live at Tschernobyl,
although - at least the offical - chances for hat type of catastrophy are
really low, with a lot of zeros between the point and the first cipher behind
the point. But, you might decide for an exciting partner,  even if  chances
are against you at .90.

Further, you can't use students t, since the 95 confidence intervall has to
be asymmetrical (the formula is given by Marascuillo/ McSweeny, 1978, and you
can easily program it, just 20 minutes C or Fortran - at least, if you don't
use windows 95).

And, you don't generalize from the sample as you did, but from the
hypothesis. And, the small and "non representative" sample might be correct
still (hennce the bias neglectable), at last, if the confunded variable does
nnot produce a so called "semi-disordinal interaction", and, and, and ... 

I still think, that Ferdinand's survey was a good idea. Because it was a
hypothesis-generating study. So, he doesn't need all the generalization stuff
you are excited about, but offers a hypothesis, which might be investigated
with all th necessary hypothesis-testing stuff, type I and type II error,
sample size, effect size, and so on.

Finally, from all LUG-users, who liked to share their M6-body-experiences on
Ferdinand's invitation, 23% claimed a broken M6 body, 77% were happy.

Hence, I still suggest, that you have an extra arangement with you local
Leica dealer, to change a broken M6 body into a new and virgin one within a
reasonable period (e.g. 4 weeks). 

It has the advantage, that now the Leica dealers will have to deal with Leitz
(not the "stupid", paying  customer), that Leitz needs to react rather quick,
and that no customer needs to wait days, or weeks, or months for a
replacement of his/her already paid M6. 

And, that his/her disappointment might be limited also. This way, Leitz might
not loose so much trust in their best :-) camera, the M6.

Alf