Push-to-web: The survey questionnaire is completed online, with the sample invited to take part through an initial postal mail out with further reminder letters and telephone chasing.
Gwthio i'r we: Mae holiadur yr arolwg yn cael ei lenwi ar-lein, gyda’r sampl yn cael gwahoddiad i gymryd rhan drwy e-bost cychwynnol, gyda rhagor o lythyrau atgoffa a galwadau ffôn.