Professor Ronald D Armstrong Department of Management Science and Information Systems Rutgers University Janice H Levin Building 94 Rockafeller Road Piscataway NJ 08854 8054 USA Dear Professor Armstrong I greatly appreciate the opportunity to strongly recommend Dr Zachary G Stoumbos for promotion to Full Professor at Rutgers University I assumed that he was already a Full Professor based on his research recognition and visibility in the academic and professional community His promotion is clearly overdue Dr Stoumbos work has been primarily in applied and industrial statistics with a major focus of his work being in statistical process control SPC and sequential analysis The numerous areas of application include manufacturing medicine management finance and law enforcement among others His recent work has expanded into innovative research in healthcare classification analysis and mathematical finance He has extensively published in top tier journals such as the Journal of the American Statistical Association Technometrics Journal of Quality Technology IIE Transactions and the two series of Nonlinear Analysis The contributions of Dr Stoumbos to SPC are major both from the technical as well as practical perspective They place him at the forefront of his field as likely the leading researcher of his generation His papers tackle very important issues in adaptive and dynamic sampling serial correlation robustness to nonnormality nonparametric methods multivariate and multiparameter SPC and process capability analysis His investigations are founded on analytical results and highly accurate numerical methods based on Markov chain modeling and stochastic integral equations with the occasional use of empirical studies when necessary I will comment on several areas of his work Traditional process monitoring methods are based on fixed samples taken at regular pre specified points in time Adaptive methods employ variable sampling rate policies in the application of control charts in order to achieve much better response rates with both standard Shewhart charts and more sophisticated CUSUM and EWMA charts see papers 7 and 20 Modern data acquisition technology now used in many applications permits further improvements in the performance achieved by the SPRT and GSPRT charts developed by Dr Stoumbos from first principles using decision methods based on dynamic sampling These control charts achieve the fastest and most reliable response rates to date Papers 32 and 33 are considered seminal on the topic They have been widely cited and have spurred significant additional research by many other engineers and statisticians on this important subject as well as numerous industrial and medical applications of this methodology This can be seen by a quick search of the Science Citation Reports Dr Stoumbos and his coauthors have brought adaptive and dynamic control chart methods from the realm of abstract theory into that of practical SPC tools that are increasingly being used by major companies such as Chevron Exxon Mobile Monsanto and General Electric and healthcare organizations and providers such as the Centers for Disease Control and Prevention Mayo Clinic and Massachusetts s General Hospital Multivariate methods have been a major deficiency in quality improvement Even though many products have multiple quality characteristics and are best studied by multivariate tools and even though multiple processes can be controlled more effectively as a whole rather than as a series of parallel uncorrelated processes practice tends to use Dr Shewhart s 1931 vintage control charts Part of the problem is inescapable there is no multivariate equivalent to the optimality of a univariate CUSUM chart but part is due to the paucity of dependable and practical multivariate methods Dr Stoumbos collection of parametric and nonparametric papers on detection and diagnosis in the multivariate arena see 1 13 17 24 and 29 makes a substantial contribution to address this major lack and even sets the record straight on some questionable popular academic methods proposed in the last ten years such as simplicial data depth His multivariate papers go a long way towards connecting with the world of practitioners who are now realizing the value of this work With the advent of the 21st century numerous companies such as General Electric Miele and Motorola and agencies such as NASA the FAA and IATA have embraced multivariate SPC and are spearheading its use One of the fundamental dogmas of SPC is the concept of rational subgroups Dr Stoumbos recent work in paper 9 with Dr Reynolds radically annuls this dogma and renders much of the conventional SPC theory and practices misguided This seminal work overturns widely adopted practices that go all the way back to the early 1930s and Dr Shewhart himself the father of SPC Thus it is gratifying that this paper won the 2004 Brumbaugh Award This prestigious award has been given annually since 1949 by the American Society for Quality ASQ for the paper making the greatest single contribution to the development and application of quality improvement It is the leading award of ASQ It is impressive that Dr Stoumbos was presented with the Brumbaugh Award in the presence of over two thousand attendees alongside distinguished awardees such as Dr S Toyoda Chairman CEO and Founder of Toyota Motor Corporation Dr F W Breyfogle III President and CEO of Smarter Solutions Inc and Dr Y Kondo Professor at MIT former Dean of Engineering at Kyoto University Japan and former President of the Japanese Society for Quality Control JSQC and the 2005 ASQ Shewhart Medalist Dr D M Hawkins Distinguished Professor at University of Minnesota Some of the strongest technical work of Dr Stoumbos can be found in a series of important papers on monitoring discrete process variables that can be modeled with Bernoulli and binomial distributions The discreteness and skewness of these variables makes traditional process control approaches ineffective In these papers exact expressions were derived and evaluated for the properties of the Bernoulli CUSUM Binomial CUSUM and SPRT charts for a proportion by modeling these charts as stochastic processes Corrected diffusion theory was used to develop convenient methods for the charts design and implementation Dr D M Hawkins Dr D C Montgomery and Dr W H Woodall three world renowned SPC researchers have noted in some of their recent articles and books that this work is particularly valuable