Don Ylvisaker

Professor Don Ylvisaker passed away peacefully on March 20, 2022. Don played a pivotal role in establishing the UCLA Department of Statistics. As head of the Division of Statistics within the UCLA Mathematics Department, he was instrumental in shaping the personality of the emerging department as one focused on not exclusively on theory, but also on teaching, consulting, and computation. Don was a Fellow of the IMS and the ASA.

Don was born in Minneapolis in 1933, and received a BA in Mathematics and Economics from Concordia College, an MA in Mathematics from the University of Nebraska, and a PhD in Statistics from Stanford. His dissertation was On Time Series Analysis and Reproducing Kernel Hilbert Spaces, with advisor Emanuel Parzen. He joined UCLA in 1968. Although he retired in 1996, he was extremely active in the department that he helped found, and, for the next ten years, rarely missed a faculty meeting or an opportunity to have coffee with his colleagues and discuss statistics, campus politics, or poker. He was known as a great teller of stories, which were often about courtroom statistical arguments, lottery oddities, games, and professional magicians.

Don’s research placed him in the center of some of the most important issues of our time, including the use of adjustments in the US Census, counting homeless people, and, indirectly at least, the O.J. Simpson trial. For many years he was a statistical consultant to the California Lottery, and advised the Lottery on a great number of issues, including ensuring random outcomes for some of their more elaborate games.

Don began his career as a mathematical statistician. At a time when computer resources were scarce and rudimentary, he specialized in stochastic processes for modeling complex phenomena. While most research in statistics deals with noisy data gathered by either observational studies or by design of experiment, a natural connection of his expertise to the complexity study in computer science gradually emerged. Don became one among the few visionary statisticians to focus on error-free data generated by computer models.

In 1984, Don presented an IMS Special Invited Lecture and published a paper entitled “Prediction and Design” (Annals of Statistics 1987). This is a subject in which he had long been interested and had made substantial contributions. The paper provided a broad framework, G-MAP (Gaussian, Markov Associated Process), for connecting a wide range of problems concerning finite observation of a stochastic process, thus presenting a fresh perspective to bridge Gaussian Markov random field, Kriging in geostatistics, infinite-dimensional estimation under reproducing kernel Hilbert space, model robust design, time series sampling, etc. His papers on design and analysis of computer experiments are among the most highly cited in the area.

Don’s writing is elegant and precise, warm, and candid. A sense of the personality of the legendary Don Ylvisaker was captured in a transcribed record of a lively dialogue with his long-term collaborator Jerry Sacks in “After 50+ Years in Statistics, An Exchange” (Statistical Science 2012). This dialogue portrays how Don’s research transformed from mathematics-driven statistics to data-driven statistics in response to the rapidly evolving world and several critical moments, including the unexpected loss of Jack Kiefer, founder of optimal design.

The current UCLA Department of Statistics was created on the foundation of Don’s view of statistics. Since 1986, the Division of Statistics in the Department of Mathematics had some autonomy in constructing its undergraduate and graduate courses, but not many resources were available for a graduate program and for statistics research. It is fair to say that Mathematics saw the importance of statistics service teaching, but it was more reluctant to prioritize statistics research, especially the data and computing centered statistics that Don envisioned. Thus, hiring statisticians who could help the Division grow grew increasingly problematic. Don became convinced that statistics at UCLA could only flourish outside the Department of Mathematics.

In 1986 the Dean of Social Sciences proposed a program to overhaul graduate teaching and research in Quantitative Methods in the Social Sciences. He also created a campus-wide committee, which included Don from the Division of Statistics, to advise in the construction of the program. Don saw an opportunity to promote a far-reaching reorganization of statistics. He made sure the persons hired into the social sciences program were data- and computing-oriented, and that the ultimate goal of the reorganization was a standalone Department of Statistics. In order to grow UCLA Statistics, he also realized it was necessary to build on the foundation of undergraduate statistics teaching. Thus, a great deal of the initial effort of the interdisciplinary group that grew out of the social science initiative focused on modernizing lower-division statistics teaching. Don was instrumental in obtaining large NSF grants to reorganize and computerize statistics teaching and research. Especially after the 1994 retirement wave in the Division of Statistics, a number of lecturers were hired into semi-permanent positions and into full participating membership in the statistics group. After more than 25 years, most of them are still here. The data emphasis in Don’s philosophy was evident in the establishment of a Statistical Consulting Center, in searching contacts with outside companies and organizations in the Los Angeles area, and in the initial moves to create a professional Master’s degree (all of this in an up-to-then non-existing department). It was also a natural outcome of Don’s view of statistics that the initial members of the new Department have degrees in a variety of disciplines, not just in statistics or mathematics. Data are everywhere. It goes without saying that subsequent developments have shown that Don’s view anticipated world-wide evolution in the discipline of statistics, even to the extent that some statistics departments now want to have “data science” in their name.

Don’s influence and personality have had a deep and lasting effect on the Department. He was a strong advocate and supporter of DataFest, and served, without fail, as a judge for the annual event, even after moving to Santa Barbara. In honor of his commitment and support, the Best Insight Award has been renamed the Don Ylvisaker Best Insight Award. Although Don’s retirement was 26 years ago, he kept close tabs on department news, communicated frequently with his colleagues, and felt to many as if he was still part of the department. His loss is deeply felt and his contributions long-lasting.

To keep Don’s memory alive in the department, the department will be giving an annual award, the Donald Ylvisaker Award for the Best Practice of Statistics, to the graduate student whose practice of statistics best reflects Don’s sense that the truth of Statistics is best expressed in real problems.

Written by Jan de Leeuw, Rob Gould, and Ker-Chau Li, Department of Statistics, University of California–Los Angeles