| Abstract: | This article describes results of the first in a series of three large-scale longitudinal studies conducted by the U.S. Employment Service to increase the usefulness of the GATB for counseling high school students. The final sample consisted of 26,708 high school students. All were tested with the GATB in 1958, and those in the lower high school grades were retested in the twelfth grade. Results were as follows: (1) Stability coefficients were highest for the eleventh grade sample and lowest for the ninth grade sample. (2) Interval between initial testing and retesting had very little relationship to size of practice effect. (3) Maturation increases were largest between the ninth and twelfth grade and smallest between the eleventh and twelfth grade. (4) OAP stability was increased through use of a “band” around the cutting scores. |
