Hi - "I Sigma I" means nothing.
<I>/<sigma(I)> is the average intensity of a group of reflections divided by the average standard deviation (sigma) of the same group of reflections. Usually its reported per resolution shell, groups of reflections within thin shells of resolution.
<I/sigma(I)> is the intensity divided by the standard deviation (sigma) of a reflection, averaged for a group of reflections. Its also usually reported per resolution shell, groups of reflections within thin shells of resolution.
Both report signal over noise, and in many (most?) publications its unclear which one is reported. They are similar but not the same.
Hope this helps. A. On 10 Dec 2008, at 23:14, ANDY DODDS wrote:
Hi, does anyone have a definition of I Sigma I please. Any definitions that i have found are not very informative for novices. thanks andy
