Let's spend some money. Was: Re: LSF method vs. averaging

[Bernard Cleyet <anngeorg@PACBELL.NET>]

I repeat:  Can we contribute $ for a system that doesn't have the
problem below?

bc, willing to pay for membership.

p.s. Did L and you all see the recent TPT article on making ones own
grating from screws?

Ludwik Kowalski wrote:

> May I suggest that you repost
> the message making lines
> shorter than you did. What
> I see has confusing = in wrong
> places and =20. For example,
>
>  we used s=imply (max-min)/2.=20
>
> This discourages some people from
> reading and guessing what to ignore.
>
> It is a pity that our server does it to
> many messages. That is why my
> lines are usually very short.
>
> The first paragraph was not clear
> to me; to measure distances between
> slits (or grooves) I would use a
> microscope not a laser. You are
> probably measuring something else
> and calculating d from it? Your first
> paragraph is too vague about the
> measurements you perform.
>
> I sense you are describing a good
> laboratory activity that many can try.
> I am looking for a good optics lab.
> Ludwik Kowalski
>
>
> On Wednesday, March 10, 2004, at 02:52 PM, Savinainen Antti wrote:
>
>
>
> > Hello,
> >
> > I have a question on data-analysis. To provide a context for my quest=
> > ion I'll briefly describe a simple lab.
> > I measured with my high school students the distance between slits (d=
> > ) for a certain grating using a laser of known wavelength. After taki=
> > ng required measurements we performed the data-analysis by calculatin=
> > g d separately for all measurements and calculated their average. Als=
> > o a rough estimate for the uncertainty of d was calculated: we used s=
> > imply (max-min)/2.=20
> >
> > Then we performed the data-analysis using a linearizion of the princi=
> > pal maxima equation (d sin(theta) =3D k * lambda) to produce a straig=
> > ht line and calculated d from the slope. This was done by utilizing t=
> > he Least Square Fit (LSF) method. The results of these two methods ag=
> > reed within the uncertainty limits.=20
> >
> > My question is the following: why is the LSF method considered to pro=
> > vide a better estimate in this particular case and also in general th=
> > an averaging? (Of course, assuming that the data fulfill the assumpti=
> > ons underlying the LSF method). I know how the LSF and weighted LSF m=
> > ethods are derived but I don't seem to find an answer to the question=
> > which would be appropriate for my high school students. Could you he=
> > lp?
> >
> > Regards,
> >
> > Antti Savinainen
> > Kuopio Lyseo High School/IB
> > Finland
> > Homepage: <http://kotisivu.mtv3.fi/physics/>