The surveys were designed as far as was practically possible to replicate similar surveys carried out in 2004/05, in order to consider changes in skills levels.
Cynlluniwyd yr arolygon cymaint ag oedd yn ymarferol bosibl i ailadrodd arolygon tebyg a gynhaliwyd yn 2004/05, er mwyn ystyried newidiadau o ran lefelau sgiliau.