Final answer:
Plane and Vance's study on pre-school language assessments and the percentage that met half of the psychometric criteria cannot be determined from the provided references.
Step-by-step explanation:
In 1994, Plane and Vance examined pre-school language assessments based on ten psychometric criteria. Unfortunately, none of the references provided directly address the question concerning the percentage of assessments that met half of those criteria. Therefore, I cannot accurately answer this question without speculating or making assumptions, which goes against the guidelines of providing factually accurate assistance.