Dear Prem, you also need to count the number of restraints as observations and constraints, which reduce the number of parameters. The number of restraints at this resolution might exceed the number of observations. If I remember correctly, the numbers are listed in the refmac5 log file and probably also in the PDB file header after refinement.
The difference between Rfree and R1 is a measure for overfitting, see https:// doi.org/10.1107/S0907444999016868 and https://doi.org/10.1107/ S0907444997013875 Best, Tim On Saturday, February 17, 2018 8:46:39 PM CET Prem Prakash wrote: > Dear all, > How observation is to parameter ratio is determined for a crystal > structure. Suppose If we have only one observation for each parameter at a > resolution of say 2.9 Angstrom, how terribly it is easy to overfitt for the > data to get a misleading agreement between model and experiment ? Is there > any thumbrule for this ratio, and how it is dependent on the resolution of > the data. Please shed some light on these aspects. > Thank you > With kind regards > Prem -- -- Paul Scherrer Institut Tim Gruene - persoenlich - OFLC/104 CH-5232 Villigen PSI phone: +41 (0)56 310 5297 GPG Key ID = A46BEE1A
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