Re: [ATM] FigureXP - monte carlo analysis

["Bob May" <rmay@nethere.com>]

Sorry, but I'd assumed that you'd be doing all of the reading
sets with the center zone at the "0" spot on the dial.  Those
Dial Indicators do allow for the scale to be turned by turning
the bezel of the dial.  I always find the 0 and then set the dial
so that it reads 0.
When you do put in random starts to a Monte Carlo routine, you do
indeed get a lot of strangeness.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: Mark Cowan <toolontop@yahoo.com>
To: <atm@atmlist.net>
Sent: Saturday, May 17, 2008 12:16 AM
Subject: Re: [ATM] FigureXP - monte carlo analysis


> Totally true, but having tested the Monte Carlo analysis in
FigXP shows that it
> doesn't normalize the readings before calculating the SD - so
if you have an
> overall spread of say 5mm and you adjusted the tester by 1mm in
between runs
> you get a SD for estimation purposes of 1mm - not the .01 to
.05mm spread in
> the relative readings.
>
> Best,
> Mark
>
> --- Bob May <rmay@nethere.com> wrote:
>
> > Systematic errors like making all of the readings several
> > thousandths of an inch off in one direction won't matter.
The
> > end error is so small that the shape of the surface will
> > completely wash them out.  Two thou over the hundrred inchs
or so
> > is a real small error.
> > Bob May
> >
> > rmay at nethere.com
> > http: slash /nav.to slash bobmay
> > http: slash /bobmay dot astronomy.net
> >
> > ----- Original Message -----
> > From: Mark Cowan <toolontop@yahoo.com>
> > To: <atm@atmlist.net>
> > Sent: Thursday, May 15, 2008 10:08 PM
> > Subject: Re: [ATM] FigureXP - monte carlo analysis
> >
> >
> > > Hey Mitch,
> > >
> > > The Monte Carlo analysis doesn't account for systematic
bias in
> > testing,
> > > unconscious or otherwise.  If you add significant
systematic
> > bias to a random
> > > distribution you still have systematic bias, thus
unrecognized
> > errors.  In such
> > > cases (which for various reasons I think reflect the
majority
> > of manual
> > > measurements of mirrors) there's no "guarantee" at all -
just a
> > WAG.  Perhaps a
> > > slightly better informed WAG, though. ;)
> > >
> > > If you do want to use the one in FigXP and you have a lot
of
> > data sets (the
> > > only way it's useful) note that the readings need to be
> > normalized first - ie,
> > > if you setup more than once, bumped the tester, or thermal
> > drift changed the
> > > baseline you need to manually adjust the numbers so that
they
> > all look like the
> > > same session - otherwise its calculation is goofy.
> > >
> > > I'd like to hear other opinions on this, these are just my,
uh,
> > random
> > > thoughts.
> > >
> > > Best,
> > > Mark
>
>
>
>
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>

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