  Auditing is a widely used method for quality improvement, and many guidelines
are available advising on how to draw samples for auditing. However,
researchers or auditors sometimes find themselves in situations that are not
straightforward and the standard sampling techniques are not sufficient, for
example when a selective sample has initially been audited and the auditor
desires to re-use as many cases as possible from this initial audit in a new
audit sample that is representative with respect to some background
characteristics. In this paper, we introduce a method that selects an audit
sample that re-uses initially audited cases by considering the selection of a
representative audit sample as a constrained minimization problem. In addition,
we evaluate the performance of this method by means of a simulation study and
we apply the method to draw an audit sample of establishments to evaluate the
quality of an establishment registry used to produce statistics on energy
consumption per type of economic activity.
