Twelve Prune Audience

A delightful description of the late mathematician John Tukey's style, from a biographical essay by Peter McCullagh FRS ("John Wilder Tukey"):

John Wilder Tukey was a scientific generalist, a chemist by undergraduate training, a topologist by graduate training, an environmentalist by his work on Federal Government panels, a consultant to US corporations, a data analyst who revolutionized signal processing in the 1960s, and a statistician who initiated grand programmes whose effects on statistical practice are as much cultural as they are specific. He had a prodigious knowledge of the physical sciences, legendary calculating skills, an unusually sharp and creative mind, and enormous energy. He invented neologisms at every opportunity, among which the best known are 'bit' for binary digit, and 'software' by contrast with hardware, both products of his long association with Bell Telephone Labs. Among his legacies are the fast Fourier transformation, one degree of freedom for non-additivity, statistical allowances for multiple comparisons, various contributions to exploratory data analysis and graphical presentation of data, and the jack-knife as a general method for variance estimation. He popularized spectrum analysis as a way of studying stationary time series, he promoted exploratory data analysis at a time when the subject was not academically respectable, and he initiated a crusade for robust or outlier-resistant methods in statistical computation.


My first recollection of Tukey comes from a 1977 visit to London, when Tukey was invited to give a seminar at Imperial College. I was a graduate student at the time, and Tukey was well known to all the students, if only by his colossal reputation. A sense of excitement and curiosity was detectable among the staff and graduate students because this was not an ordinary seminar. An extra-large parade of local luminaries occupied the front row, and the graduate students as usual were safely ensconced in the rear. After his introduction, Tukey ambled to the podium, a great bear of a man dressed in baggy pants and a black knitted shirt. These might once have been a matching pair, but the vintage was such that it was hard to tell. An array of coloured pens bulged from his shirt pocket. These, I later learned, are essential tools for data analysis Tukey style.

Carefully and deliberately, a list of headings was chalked on the blackboard. The words came too, not many, like overweight parcels, delivered at a slow unfaltering pace. For the most part, the words were familiar individually, but as phrases they seemed strangely obscure. What did they mean? Was it English? I had no idea, but I was only a graduate student. Surely someone must know, someone in the front row. The list was not long, but seemed to take a long time to write. When it was complete, Tukey turned to face the audience and the podium, a long desk of the type used for demonstrating chemistry or physics experiments. 'Comments, queries, suggestions?' he asked the audience, each word seeming to take a full minute to deliver. As he waited for a response, he clambered onto the podium and manoeuvred until he was sitting cross-legged facing the audience. This activity must have taken a full minute, but there was still no response. As he sat there in a perfectly relaxed Buddha pose, it became apparent that Tukey was in no hurry to deliver his message, whatever it was. He seemed no more ill at ease than if he were at the beach or a baseball game. We in the audience sat like spectators at the zoo waiting for the great bear to move or say something. But the great bear appeared to be doing the same thing, and the feeling was not comfortable. How long could this go on, we wondered. After a long while, as if to confirm the position, he extracted from his pocket a bag of dried prunes and proceeded to eat them in silence, one by one. The war of nerves continued ... four prunes, five prunes.... How many prunes would it take to end the silence? The situation demanded leadership, so we looked anxiously to the front row for relief. Still no response ... eight prunes, nine prunes.... Several prunes later he had had enough, so he passed the remainder in silence to the would-be audience, now spectators. After what seemed like an eternity, someone from the front row asked a safe question: 'John, could you explain what you mean by such and such.'

That was all that was required, and the seminar then continued relatively uneventfully with active participation from the front row. As I later came to understand, anyone who thought that the speaker might cave in first did not know John Tukey. The prunes undoubtedly had a simple dietary explanation, but to some in the audience it seemed that he had instituted his own private classification of seminar audiences, and we were a 12-prune audience.

(cf KWICS, Chinks, and Chunks (2000-01-31), John Tukey (2000-07-31), ...) - ^z - 2022-11-13