[phenixbb] phenix and weak data

Pavel Afonine pafonine at lbl.gov
Mon Dec 10 13:08:52 PST 2012

Hi Ed,

>>> I had always assumed that experimental sigmas were somehow lumped
>> into the alpha and beta parameters (esp. given your discussion in
>> section 2.3).  In principle they could be, right?
>> Yes, they could be.
> I would like clarification on this.  (...)
> Alpha/beta are calculated in individual resolution shells.  How can you
> "lump" experimental variance that varies by two orders of magnitude for
> individual reflections into a single parameter?

I'm sorry for being unclear (often email happens to be a poor way to 
express what you actually mean, unless you have heaps of time to write 
it lawyer style. There is always a room for reader to imagine unsaid. 
Sometimes it works, sometimes it doesn't.).

Anyways, extending my phrase above to better reflect what I actually 
meant: "Yes, they could be, to some extent (approximation). Surely, a 
proper way is to have sigmas in the formula explicitly, as I stated in 
previous email of that thread. Whether that makes any practically useful 
difference is debatable, and yet to answer."

> I also wonder if introducing experimental uncertainty into Lunin's ML
> target is even possible without fundamentally altering it.

It is possible, and depends how fundamentally you want to alter it.

All the best,

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