The questionnaire used for the second round of fieldwork was largely kept the same as the first so that data from the two rounds could be combined into a single data set.
Cadwyd yr holiadur a ddefnyddiwyd ar gyfer yr ail rownd o waith maes i raddau helaeth yr un fath â'r cyntaf er mwyn gallu cyfuno data o'r ddwy rownd yn un set ddata.