COLUMBIA — Even after several heart surgeries within 20 years and a decade into his retirement, Robert K. Tsutakawa continued to work tirelessly, a former colleague said.
"Every six years, he had some kind of surgery, but he always recovered," said Dongchu Sun, a former colleague of Tsutakawa and current chair of MU's department of statistics. "He had a big one three or four years ago." Still, Sun said, "he swam everyday."
Mr. Tsutakawa died Saturday, Jan. 28, 2012, at John Muir Medical Center in Concord, Calif. He was 81.
He was born on March 28, 1930, in Seattle to Joji and Yachiyo Tsutakawa. In 1961, he married Teruko Tsujihara.
Mr. Tsutakawa taught statistics at MU from 1968 until his retirement in 1997. He served as the statistics department chair from 1989 to 1995.
"He was a wonderful person, personally and professionally," Sun said. "Very friendly."
Sun and Mr. Tsutakawa met in 1991, when Sun was a graduate student at Purdue University and attended a conference at MU.
Mr. Tsutakawa "was very good in three areas," Sun said. The areas included experimental design, hierarchical modeling and item response theory, to which he made significant contributions that gave him worldwide recognition.
By using a new method, Mr. Tsutakawa mastered the process of identifying the difficulty level of each question, or item, on a standardized test. Whether the creators of widely used tests such as the GRE, ACT or SAT used certain questions on their exams "were based on Bob's contributions," Sun said.
Mr. Tsutakawa retired in 1997, but that didn't stop him from continuing to help his students succeed.
"He was very active even after retirement," Sun said. "He was here for another 10 years."
For two years, Mr. Tsutakawa and Sun mentored Hoon Kim, who is now a professor of mathematics and statistics at Cal Poly Pomona.
That help, however, wasn't only offered to students. Mr. Tsutakawa extended his hand even to his colleagues, including Sun.
"He was a gentleman," Sun said. "He would consider your perspective. When I came over here (to Missouri), my wife didn't come with me the first year, so he helped me a lot getting around Columbia and finding a place to stay. He was very helpful."
This week, the department of statistics will form the Robert Tsutakawa Memorial Fund "to remember his contributions to the department and the profession," Sun said. The fund will benefit the statistics department and its students.
Sun said he will remember Mr. Tsutakawa as a respected colleague and friend.
"He was always kind of fun to be with," Sun said. "He always smiled. Anything difficult would be easier after talking to him. He would say, 'I'm sure you can do it' as an encouragement."
Mr. Tsutakawa was a member of the American Statistical Association, the Institute of Mathematical Statistics, the Biometric Society and the American Educational Research Association.
He also served as the associate editor of the "Journal of Educational Statistics," a globally recognized publication, from 1983 to 1989 and as its editor from 1990 to 1992.
In recent years, Mr. Tsutakawa lived in Lafayette, Calif., to be with his children.
His wife and his brother James died earlier.
He is survived by two sons, Bert Tsutakawa of Seattle and John Tsutakawa of San Francisco; a daughter, Susan Tsutakawa of Dublin, Calif.; a sister, Marion Kanemoto of Sacramento, Calif.; a brother, Richard Tsutakawa of Lafayette, Calif.; and three grandchildren.
Services will be held at 2 p.m. Friday at Oakmont Memorial Park & Mortuary, 2099 Reliez Valley Rd., Lafayette, CA 94549.