As digital technology flourished, modes of interaction pertaining to computer systems started to be utilized in consumer products. As a consequence, problems peculiar to software began to be observed in once simple-to-operate products. In order to overcome these problems, one of the most versatile tools utilized during design and evaluation stages in software development, that is usability testing, was introduced to the domain of consumer products. However, both literature findings and author"s personal experiences show that there are some problems with sampling issues, since participants" prior experiences with digital interfaces seem to affect test results more in the case of consumer products. In this study, after a theoretical discussion, the measurement tool being developed to control general interaction expertise (GIE) was presented. In the preliminary studies of predictive validity, correlation coefficients up to 0.76 were detected between test scores and usability performance.