The effect of guardbands on errors in production testing

Guardbands are often used in production testing when instrumentation inaccuracies are present. Guardbands protect against the error of inadvertently certifying a defective product to be good. Unfortunately, guardbands also increase the amount of good products that are erroneously failed in testing. This paper analyzes the testing error trade-offs due to guardband placement for the case when a manufacturing process has a specific design objective (a target) to meet. The analysis shows how to quantify the effects of the errors due to guardband placement in terms of (1) the fraction of defective product shipped to a customer and (2) the fraction of good products failed and discarded. An example is presented that illustrates how to estimate the economic consequences of errors in testing