The verification of compliance with a particular undertaking by use of on-site inspection is often influenced by considerations of timeliness. Brief but frequent visits may need to be made at regular or irregular intervals between more exhaustive inspections in order to obtain, with some degree of assurance, short notice indication of a possible violation. In Chapter 7 we shall be considering the problem of timely detection in the context of material accountancy under the Nuclear Weapons Non-Proliferation Treaty (NPT), where measurement uncertainties and the associated probabilities of false alarm play the decisive role. In the present chapter we treat a simpler NPT verification problem, very analogous to the attributes sampling problem of Section 2.2. In fact, this chapter might have been given the title Attributes Sampling over Time.

Interim inspections for timely detection generally involve excessive demands on travel expenses and manpower resources for the inspecting party, so it's of interest to look for inspection strategies which optimize timeliness under given constraints. Our optimization criterion will therefore be the expected time to detection of violation, rather than detection probability.

To illustrate, a fairy tale (Canty and Avenhaus (1991)):

The Inspector who got Something for Nothing

Once upon a time there was an inspector who wanted to spend more time with his family.