**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

The permitted range is [0.0, infinity)

**Related item: **_refine.ls_goodness_of_fit_obs (alternate)

**Category:** refine

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