Mark K. Snell

Small-Sample Confidence Intervals for p 1– p 2 and p 1/p 2 in 2 × 2 Contingency Tables

Abstract Consider two binomial populations II1 and II2 having “success” probabilities p 1 in (0, 1) and p 2 in (0, 1), respectively. This article studies the problem of constructing small-sample confidence intervals for the difference of the success probabilities, Δ = p 1 – p 2 and their ratio (the “relative risk”), ρ = p 1/p 2 based on independent random samples of sizes n 1 and n 2 from II1 and II2, respectively. These are nuisance parameter problems; hence the proposed intervals achieve coverage probabilities greater than or equal to their nominal (1 – α) levels. Three methods of constructing intervals are proposed. The first one is based on the well-known conditional intervals for the odds ratio ψ = p 1(1 – p 2)/p 2(1 – p 1). It yields easily computable Δ and ρ intervals. The second method directly generates unconditional intervals of the desired size. An algorithm is given for producing the intervals for arbitrary n 1 and n 2. The 2 × 2 case is given as an illustrative example. The third method const...

Discrete-event simulation for the design and evaluation of physical protection systems

Explores the use of discrete-event simulation for the design and control of physical protection systems for fixed-site facilities housing items of significant value. The paper begins by discussing several modeling and simulation activities currently being performed in designing and analyzing these protection systems and then discusses the capabilities that design/analysis tools should have. The authors then discuss in detail how some of these new capabilities have been implemented in software to achieve a prototype design and analysis tool. The simulation software technology provides a communications mechanism between a running simulation and one or more external programs. In the prototype security analysis tool, these capabilities are used to facilitate human-in-the-loop interaction and to support a real-time connection to a virtual reality model of the facility being analyzed. This simulation tool can be used for both training (in real-time mode) and facility analysis and design (in fast mode).

Distributed real-time simulation for intruder detection system analysis

The paper describes a distributed simulation system developed for evaluation of physical security systems. The work extends previous work by extracting several system components that were previously integrated into the simulation model and creating distributed modules that interact directly with the system database. This allows the modules to incorporate arbitrarily complex logic and to be developed without detailed knowledge of the structure or language to implement the principal simulation component.

Leveraging Safety Programs to Improve and Support Security Programs

There has been a long history of considering Safety, Security, and Safeguards (3S) as three functions of nuclear security design and operations that need to be properly and collectively integrated with operations. This paper specifically considers how safety programmes can be extended directly to benefit security as part of an integrated facility management programme. The discussion will draw on experiences implementing such a programme at Sandia National Laboratories’ Annular Research Reactor Facility. While the paper focuses on nuclear facilities, similar ideas could be used to support security programmes at other types of high-consequence facilities and transportation activities.