Data quality: Difference between revisions

59 bytes added ,  10 February 2008
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changed to greek letter sigma
(New page: == What is the resolution of my dataset? == First of all, it is limited by completeness. In practical terms this means that the highest resolution you can get is the resolution at the ed...)
 
m (changed to greek letter sigma)
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First of all, it is limited by completeness.  In practical terms this means that the highest resolution you can get is the resolution at the edge of the detector.  If you collected enough frames, you may be able to squeeze out 0.1A if you process data all the way to the corner.  Usually the detector is positioned close enough to the crystal so that you don't have any diffraction at the edge and then resolution limits should be chosen based on strength of the diffraction.   
First of all, it is limited by completeness.  In practical terms this means that the highest resolution you can get is the resolution at the edge of the detector.  If you collected enough frames, you may be able to squeeze out 0.1A if you process data all the way to the corner.  Usually the detector is positioned close enough to the crystal so that you don't have any diffraction at the edge and then resolution limits should be chosen based on strength of the diffraction.   


This limit is commonly based on average I/sigma.  Examples of such choices are:
This limit is commonly based on average <math>I/\sigma</math>.  Examples of such choices are:


- I/sigma=1 in the highest resolution shell


- I/sigma=2 in the highest resolution shell
- <math>I/\sigma=1</math> in the highest resolution shell


- at least 50% of reflections in the highest resolution shell have I/sigma>2
- <math>I/\sigma=2</math> in the highest resolution shell
 
- at least 50% of reflections in the highest resolution shell have <math>I/\sigma</math> > 2


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