Dear Radovan,
At 05:08 PM 4/9/01 +0200, you wrote:
>Bob Von Dreele wrote:
>
> >The only exception to this is profile measurements taken on a film
> or >image plate where one observation may "bleed over" onto
> neighboring >ones. Only in that case are the profile points correlated
> with each >other in a statistical sense.
>
> > Bob Von Dreele
>
>In that case even the single crystal data resulting from the integration
>of images registred by an image plate are not strictly independent!!??
>Information read from one pixel can depend on the information registred
>in a neigbouring pixel.
This would be true if the spots are close enough to each other so that they
overlap (i.e. in protein patterns). Another case is that of 2-D area
neutron detectors where one strong reflection can interfere with the
measured intensities of other reflections seen in the same crystal setting
because it can "blind" the whole detector. The main point is that one
observation must somehow be correlated in the measuring process with other
observations for them to not be statistically independent. The fact that
the suite of observations are of the same object whether it be Bragg peaks
in a powder pattern or some other experimentally observed feature does not
make these observations "correlated". Bottom line is that Hamilton's test
is just as valid for powder data as it is for single crystal data.
Bob Von Dreele
>--
>Radovan Cerny
>Laboratoire de Cristallographie
>24, quai Ernest-Ansermet
>CH-1211 Geneva 4, Switzerland
>Phone : [+[41] 22] 702 64 50, FAX : [+[41] 22] 702 61 08
>mailto : [EMAIL PROTECTED]
>URL : http://www.unige.ch/crystal/cerny/rcerny.htm
