All non-participating LAs were contacted about an interview, and the 6 interviews completed were with those who agreed to take part, therefore there is likely to be self-selection bias.
Cysylltwyd â phob ALl nad oedd yn cymryd rhan am gyfweliad, ac roedd y 6 chyfweliad a gwblhawyd gyda'r rhai a gytunodd i gymryd rhan, felly mae'n debygol y bydd gogwydd hunan-ddethol.