A 3-D contingent scaffolding model of a hypermedia system is proposed which gradually weans learners off the technical support of instructors or more knowledgeable peers as they master certain skills. The model permits the instructor to vary his or her support in response to the learner's performance in a learning task consisting of a sequence of steps/sub-tasks. This paper reports on the implementation of this model in a computer-based instruction program at Purdue University (Indiana) and on a study of its effectiveness. The 3-D contingent scaffolding model in this study is implemented in a computer-based instruction program, "Hypothesis Testing--the Z-Test" in order to establish baseline data for integrated media-based instruction or hypermedia-based learning environment. Findings show evidence that this program does indeed promote knowledge retention and improve independent learning. (Contains 14 references.) (AEF)