To help them do this, interviewers are provided with background information on some of the questions at the interviewer briefings that take place before fieldwork begins.
Er mwyn eu helpu i wneud hyn, caiff y rhai sy'n cyfweld wybodaeth gefndir am rai o'r cwestiynau yn y cyfarfodydd briffio a gynhelir cyn dechrau ar y gwaith maes.