Am 04.03.2011 11:11, schrieb Kay Diederichs:
> There is nothing wrong with R_meas of 147.1% since, as others have said,
> R_meas is not limited to 59% (or similar) as a refinement R-factor is.
> Rather, R_meas is computed from a formula that has a denominator which
> in the asymptotic limit (noise) approaches zero - because there will be
> (almost) as many negative observations as positive ones! (The numerator
> however does not go to zero)
>
upon second thought, this explanation is wrong since the absolute value
is taken in the formula for the denominator.
A better explanation is: in the "noise limit" the numerator is (apart
from a factor>1 which is why R_meas is > R_sym) a sum over absolute
values of differences of random numbers. The denominator is a sum over
absolute values of random numbers. If the random values are drawn from a
Gaussian distribution then the numerator contributions are bigger by
square-root-of-two than the denominator contributions. Thus, R_meas can
be 150-200% .
Kay
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