The measure of performance improvement potential (Gilbert, 1978) in human performance technology uses an exemplary performance as a criterion against which to measure the potential improvement in the performance of a workforce. The measure is calculated based on the performance efficiency which compares expended resources to productivity. The same notion is used to measure the efficiency of instructional conditions, based on learners' mental effort invested in a learning task compared to their performance. This article compares the efficiency of an instructional condition for three groups of students differentiated by their use of an electronic performance support system (EPSS) to conduct a performance analysis project. The results indicated that the instruction was most efficient for those learners who showed greater competency in using the EPSS. Implications for using this technique as a means of formative evaluation of a course are discussed. (Contains 1 note, 2 tables, and 4 figures.)