Further details of the changes to survey method, sample design, estimation approaches and the effects of applied caps and recalibration are available in the ‘ GBTS Background Quality Report 2021 ’.
Mae rhagor o fanylion am y newidiadau i ddull yr arolwg, dylunio'r sampl,r dulliau amcangyfrif ac effeithiau’r capiau a ddefnyddir ar gael yn Adroddiad Ansawdd Cefndir 2021 GBDVS.