After I had started to put some of my thoughts into a first draft for this talk, I selected “The Error” as a title. This selection gave me a great deal of flexibility since, no matter how I went wrong, I was still well within the limits of the title. After additional deliberation, I had more than a slight feeling that the title was more appropriate for a potential best-seller in the field of popular fiction than it was for a potential presidential address to this society. I have, on occasion, thought that I could write–in fact, I started my academic life in a School of Journalism. At least at the academic level, the journalistic style of writing rather quickly suppressed my interest therein as a means of making a livelihood.

Errors, random and otherwise, are often the heart of some rather undercover plots and subplots in best-sellers. But just as in the case of novels, in experimental designs errors also play a dominant role–unfortunately the experimental units, which are the players, often do not understand their roles as set forth in the design script. The latter is usually in the form of a mathematical model. A question might be raised in some instances as to whether it is more difficult to teach the experimental units what the model calls for, or to teach the designer what types of designs are potentially appropriate for expressing the behavior of experimental units, under specified experimental conditions.