This means that it is not valid to compare raw scores that pupils achieve on their assessments, as each pupil sees different questions of varying levels of difficulty.
Mae hyn yn golygu nad yw'n ddilys cymharu sgoriau crai y mae disgyblion yn eu cyflawni ar eu hasesiadau, gan fod pob disgybl yn gweld cwestiynau gwahanol o ran lefelau anhawster amrywiol.