On Sunday, 8 March 2020 01:08:32 PDT Rangana Warshamanage wrote:
> "The best estimate we have of the "true" B factor is the model B factors
> we get at the end of refinement, once everything is converged, after we
> have done all the building we can. It is this "true B factor" that is a
> property of the data, not the model, "
>
> If this is the case, why can't we use model B factors to validate our
> structure? I know some people are skeptical about this approach because B
> factors are refinable parameters.
>
> Rangana
It is not clear to me exactly what you are asking.
B factors _should_ be validated, precisely because they are refined parameters
that are part of your model. Where have you seen skepticism?
Maybe you thinking of the frequent question "should the averaged refined B
equal the Wilson B reported by data processing?". That discussion usual
wanders off into explanations of why the Wilson B estimate is or is not
reliable, what "average B" actually means, and so on. For me the bottom
line is that comparison of Bavg to the estimated Wilson B is an extremely
weak validation test. There are many better tests for model quality.
Ethan
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