Roberto Battistutta wrote:
Hi,
in the Rupp book the following relation is reported (on pag 415):
Rmerge ≈ 0.8/<I/σ(I)>
referring to a relation of "the linear merging R-value with the signal-to-noise
ratio".
in a 2006 CCP4bb, Manfred Weiss reported:
Rrim (or Rmeas) = 0.8*sd(i)/I
>
Bernhard Rupp wrote:
>
> 0.8*sd(i)/I = 0.8/(I/sd(i))
>
---------------------------
Yes, but in this context it is worth pointing out that
<I/σ(I)> != 1/<σ(I)/I>
especially if there is a wide range in values of <I/σ(I)>,
which would be narrower but still significant in the outer shells.
ave(100, 10, 1) = 37
ave(0.01, 0.1, 1) = .37 = 1/(2.7) != 1/37
So while of course Rupp's equation is correct, if we try to apply it to average
values,
which we have to do to compare with Rmerge, it is no longer correct, so even at high
multiplicity the two equations quoted in original post seem incompatible.
(Unless I'm badly confused again)
eab
