The standard plan for the assessment of the variation due to a measurement system involves a number of operators repeatedly measuring a number of parts in a balanced design. In this article, we consider the performance of two types of (unbalanced) assessment plans. In each type, we use a standard plan augmented with a second component. In type A augmentation, each operator measures a different set of parts once each. In type B augmentation, each operator measures the same set of parts once each. The goal of the paper is to identify good augmented plans for estimating the gauge repeatability and reproducibility (GR&R), a ratio that compares the contribution of the measurement system to the overall process variation. We show that, if there are three or more operators or if we include the possibility of part-by-operator interaction, then use of an appropriate augmented plan can produce substantial gains in efficiency for estimating GR&R compared with the best standard plan with the same total number of measurements.
Stevens, N.T., Browne, R., Steiner, S.H. & MacKay, R.J. (2010). Augmented measurement system assessment. Journal of Quality Technology, 42(4), 388–399.