In many cases the same or similar questions have been asked before and are available from the National Statistics harmonised question set or from other question banks.
Lle bynnag y bo'n bosibl, dewisir cwestiynau sydd eisoes wedi cael eu defnyddio mewn fersiynau blwyddyn lawn o’r Arolwg Cenedlaethol ac mewn arolygon mawr eraill.