Variables acceptance sampling plans are designed under the assumption that measurement on the characteristic of interest may be performed without error. To the contrary, variables measurement tasks are often confounded by human inspection error and/or instrument test error. The net result may be characterized in terms of bias and imprecision, where (1) bias is the difference between the true dimension of a unit of product and the average of a long series of repeated measurements on that unit, and (2) imprecision is the dispersion of repeated measurements on the same unit of product.