|
INTERNATIONAL TABLES for CRYSTALLOGRAPHY |
Volume G |
Definition and Exchange of Crystallographic Data |
Definition:
The least-squares goodness-of-fit parameter S for
significantly intense reflections (see
_reflns.threshold_expression) after the final cycle of
refinement. Ideally, account should be taken of parameters
restrained in the least-squares refinement. See also
_refine.ls_restrained_S_ definitions.
{ sum { w [ Y(obs) - Y(calc) ]^2^ } }^1/2^
S = { ----------------------------------- }
{ Nref - Nparam }
Y(obs) = the observed coefficients
(see _refine_ls_structure_factor_coef)
Y(calc) = the calculated coefficients
(see _refine_ls_structure_factor_coef)
w = the least-squares reflection weight
[1/(u^2^)]
u = standard uncertainty
Nref = the number of reflections used in the refinement
Nparam = the number of refined parameters
and the sum is taken over the specified reflections
Type: float
Mandatory item: no
Alias:Related item: _refine.ls_goodness_of_fit_obs (alternate)
Category: refine
Copyright © 2005 International Union of Crystallography