Re: [Phys-l] projectile motion lab

[Jack Uretsky <jlu@hep.anl.gov>]

NOW, you tell me!  Were  you previously giving me a homework assignment?
					Jack



On Wed, 11 Oct 2006, Bernard Cleyet wrote:

> The book to which I referred does that, quite clearly and here it is:
> [UC for italics]
>
> 4.4 The SD of the Mean
>
> If X1 ....., Xn are the results of N measurements of the same quantity
> X, then, as we have seen, our best estimate of the quantity X is their
> mean, X bar.  We have also seen that the SD sigma x characterizes the
> average uncertainty of the separate measurements X1, .... Xn.  However,
> our answer X best = X bar represents a judicious combination of all N
> measurements, and there is every reason to think it will be more
> reliable  than any one of the measurements considered separately.  In
> Chapter 5 we will prove that this is so;  the uncertainty in the final
> answer X best = X bar turns out to be the SD, sigma x,  DIVIDED BY SQRT
> (N).  This quantity is called the SD OF THE MEAN, and is denoted by
> sigma x bar.
>
> eq. 4.14  :    sigma x bar = sigma x / sqrt (N)
>
> (Other common names for this are STANDARD ERROR and STANDARD ERROR OF
> THE MEAN)  Thus ......
>
> Proof referred to above on pp. 127-130
>
> bc tired of copy typing.
>
> Jack Uretsky wrote:
>
> > Hi Tim-
> > 	Does one of the references distinguish - I repeat - distinguish
> > between "standard deviation" and "standard deviation of the mean" ?
> > If so, could you kindly tell me which one?
> > 				Regards,
> > 					Jack
> >
> > On Tue, 10 Oct 2006, Folkerts, Timothy J wrote:
> >
> >
> >
> > > > Can someone direct me to an authoritative work on statistics
> > > > that distinguishes between "standard deviation" and
> > > > "standard deviation of the mean" ?
> > >
> > > How about NIST?  They have a great online applied stats references.
> > >
> > > Here is a general discussion of error analysis
> > > http://www.itl.nist.gov/div898/handbook/mpc/section5/mpc5.htm
> > >
> > > Here is a bit on confidence intervals for means, which mentions "standard error".
> > > http://www.itl.nist.gov/div898/handbook/eda/section3/eda352.htm
> > >
> > > Or read the glossary for a quick (although rather dense) definition for "standard error"
> > > http://www.itl.nist.gov/div898/handbook/glossary.htm
> > >
> > >
> > > Tim Folkerts
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