# Core CIF Dictionary version 2.3

# _refine_ls_goodness_of_fit_ref

### Name

`'_refine_ls_goodness_of_fit_ref'`
**Category:** refine

**Data type:** numb
(with optional s.u. in parentheses)

**Enumeration range:** 0.0 -> infinity

### Definition

The least-squares goodness-of-fit parameter S for all
reflections included in the refinement, after the final cycle
of refinement. Ideally, account should be taken of parameters
restrained in the least squares. 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

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