Gall cyfanswm y data perfformiad sydd ar gael beri dryswch. Er bod y tudalennau gwe yn cynnig llawer o wybodaeth i gefnogi craffu manwl, nid y bwriad yw iddynt fod yn unig ffynhonnell. Mae’r tudalennau’n cynnwys dolenni i ffynonellau eraill o wybodaeth a fydd o gymorth i’r sawl sydd â diddordeb mewn dadansoddi amrywiad mewn perfformiad, neu sydd â dyletswydd i wneud hynny. Eu bwriad hefyd yw helpu i hwyluso trafodaeth.
The abundance of performance data can be confusing.  Whilst the webpages will provide considerable information to support robust scrutiny, they are not intended to be the only source.  The pages include links to other sources of information which will help those who have an interest in, or duties which involve, analysing performance variation.  They are also intended to help to facilitate debate.