checkCIF procedure
PLAT089
PLAT089 Type_3 Test for reasonable Data / parameter ratio (non-centro) (Zmax < 18)
The data/parameter ratio should in general be higher than 7 for a quality determination of a structure containing atoms with Z less than 18. This ratio can be improved by not refining C-H parameters other than riding on their carrier atom. Note: The number of reflections used in this ratio is the number obtained by Laue group averaging.