ILLINOIS UNIV AT URBANA-CHAMPAIGN COMPUTER-BASED EDUCATION RESEARCH LAB
A computerized diagnostic adaptive test for a series of pre-algebra signed-number lesson which are also on the computer system was programmed along with a computer-managed routing system by which each examinee was sent to the instructional unit corresponding to the level of skill at which shehe stopped in the initial test. Upon completion of the course a computerized conventional posttest was given to the examinees. The posttest scores were far from being unidimensional, while the pretest and posttest data obtained from a previous study, in which the pretest was a computerized conventional test and students were forced to go through all instructional units regardless of their achievement in the pretest, indicated a strong tendency to be unidimensional. The response patterns of the posttest in the present study showed a high error rate for the skills prior to stopping levels for a subgroup of examinees. A cluster analysis was performed on the response patterns and four different groups were found. A discriminant analysis indicated significant differences among the four groups in response patterns of the skills in signed number operations. After interviewing the teachers and several children, we came to the conclusion that it was the difference between prior and current instructional methods that confused students and caused a mess in the posttest data, i.e., there was a proactive inhibition effect.