A method is described for measuring workpieces, each having structural features that form test features for measurement. The method determines an unstable one and a stable one of the test features, based on expected violation or satisfaction, respectively, of a statistical control rule. The method measures workpieces such that the unstable test feature is measured more frequently than the stable test feature. The method ascertains whether the unstable test feature remains unstable and whether the stable test feature remains stable. The method measures additional workpieces if the unstable test feature remained unstable and the stable test feature remaining stable. The determining is repeated if the unstable test feature is no longer unstable, the stable test feature is no longer stable, or any other measurement feature changes, such as if a new batch of workpieces is to be measured, environmental conditions change, or measurement has proceeded longer than a predefined threshold.