William Scott wrote:
I am not sure what to expect - there will be no Fh" calculated
contribution for a centric reflection, so the Lack of closure should
remain equal to the "observed difference" ( which also SHOULD be 0, but
may not be..) and therefore I would expect Cullis R either to be 1 or
undetermined. In MLPHARE I dont think any calculation will be carried
out - I think it tests for centric or acentric before accumulating stats..
But either way - it isnt a meaningful statistic!
Eleanor
Dear Eleanor:
I don't have the data set in front of me, but if the lack of closure
were,
say, 0.5, and the measured centric differences were slightly different
(say by 3 %), presumably the denominator would be very small, and then
the fraction would become larger than 1. The closer the measured
difference gets to the real difference (0), the larger the fraction then
becomes.
I'm assuming at least one centric reflection is mis-phased, so the lack
of closure error could then be other than 0 for centrics.
Many thanks.
Bill
On Fri, 19 May 2006, Eleanor Dodson wrote:
I cant see how you can have an anomalous Cullis R > 0 for centrics.
It is
Lack_of_closure/ Observed_Difference.
Maybe when the data was processed you have a residual Anom_diff which
should be 0 but has been kept as a measure of error or something? If
so I guess it could be 1?
Eleanor
William Scott wrote:
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Hi everyone:
How is an anomalous Cullis R defined for centric reflections? (If
it is the F+ - F-, how can that be meaningful?)
Thanks.
Bill Scott
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