Ratio developmental quotients from the Bayley are comparable to later IQs from the Stanford-Binet.

Ratio developmental quotients (DQs) from Bayley Scales administered after age 30 months were compared to Stanford-Binet IQs secured later. Means from two testings of 42 mentally retarded children were almost identical. The DQs and IQs correlated .81, p less than .001. These findings justify the use of Bayley ratio quotients to determine intellectual level of children who are too old for the Bayley norms but too retarded to earn a basal level on the Stanford-Binet.