Siegfried Heiler is one of the founding fathers of the Faculty of Statistics at the Technical University (formerly University) of Dortmund, the only one of its kind in the entire German-speaking area. Otherwise, statistics is taught in Germany at many faculties (mathematics, medicine, economics, sociology, psychology) as a minor subject, so to speak. But when, at the end of the 1960s, Dortmund was about to establish its second university in the Ruhr region alongside Bochum, it took a leaf out of the book of American elite universities, all of which have their own Department of Statistics, and Siegfried Heiler was there from the very first semester, representing the subjects of statistics and econometrics. As a trained economist, he had obtained his doctorate in 1967 in Tübingen with Heinrich Strecker on the analysis of the structure of economic processes by decomposition of time series and had then moved to the TU Berlin. There he was significantly involved in the so-called Berlin method, a method for the seasonal adjustment of time series that is still used today and has often been applied in practice. This topic of time series analysis, which he had already touched upon in his doctoral thesis, was to remain the focus of his scientific interests throughout his life. In addition to methods of seasonal adjustment, Siegfried Heiler also presented papers on - among other things - causal filters, spline functions in the estimation of spectral densities, or the robust estimation of ARMA models.
After his habilitation with Kurt Weichselberger in 1970, Siegfried Heiler worked briefly as a professor at the Technical University of Berlin before accepting a call to the University of Dortmund, where he was appointed full professor on December 14, 1972. Together with Friedhelm Eicker (the first professor of statistics in Dortmund), Franz Hering and Siegfried Schach, he was part of the founding quartet of what was then called the "Department" of Statistics. He remained in Dortmund until 1987, when he accepted another appointment at the University of Konstanz, where he taught at the Faculty of Economics and Statistics until his retirement in 2007 and was also involved in the Konstanz DFG Collaborative Research Center 178: "Internationalization of the Economy".
In addition to his scientific work, Siegfried Heiler also took the infrastructural tasks associated with science very seriously. He was twice, from April 1975 to the end of March 1976, and from April 1979 to the end of March 1980, Dean of the Faculty of Statistics and from April 1980 to the end of March 1981 its Vice-Dean. He was also very active in the German Statistical Society, serving from 1980 to 1988 as head of the committee on "Statistical Theory and Methodology," and from 1988 to 1992 as its chairman elected by the members. From 1992 to 1996, he continued to be associated with the German Statistical Society as vice-chairman and then as a regular visitor to the Statistical Week. On his 84th birthday, October 20, 2022, he passed away after a long illness. His colleagues and staff at TU Dortmund University will forever honor his memory.