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
