After controlling for a range of other factors that might have played a part (mother’s educational level, overcrowding, low birth weight, parent a poor reader, etc.),
Ar ôl ystyried ystod o ffactorau eraill a allai fod wedi dylanwadu ar blant (lefel addysgol y fam, gorboblogi’r tŷ, pwysau geni isel, rhiant sy'n ddarllenydd gwael, etc.),