Forms I and II of the Arthur Performance Scales with mental defectives

When administered to 2 groups of mental defectives, discrepant MA scores were yielded by Forms I and II of the Arthur Performance Scale. Factors accounting for the difference are discussed. Form I is to be preferred as a more accurate test. 3 other tests were appraised as unsuitable for accurate estimations of levels of ability in mental defectives. Form II of the Arthur Performance Scale was not considered an accurate instrument, and should be restandardized with a "more adequate sampling in the defective range."