Educators often use manipulatives when teaching mathematics because manipulatives are assumed to promote learning. However, research indicates that instructional variables impact the effectiveness of manipulatives. In this article, the authors consider the relations between two instructional characteristics: (a) level of instructional guidance and…

A two-step control procedure is demonstrated in which the experimenter first identifies the most appropriate control group for the investigation and then employs multiple covariates to adjust the dependent measure(s) for these sources of error. This procedure is demonstrated in a learning strategy experiment. (GK)