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\noindent{\bf William John YOUDEN}\\
b. 12 April 1900 - d. 31 March 1971
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\noindent{\bf Summary.} Beginning with the balanced incomplete block 
designs known as Youden
Squares, W. J. Youden created many designs tailored to the needs of the
physical and engineering sciences.
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Jack Youden, the great communicator of statistical ideas and
practicies in non-statistical terms, was born on April 12, 1900, in
Townsville, Australia.  He came to the U.S.A. at the age of seven
and was trained as a chemist (Ph.D., Columbia University, 1924).  A
few years into his career, however, he became convinced that
statistical methods are indispensable in all scientific work, for
efficiency and validity.  His contributions as a ``missionary" for
statistics in scientific research were so impressive that the
statistical societies gave his name to three series of awards and
prizes:

\noindent (i) The Youden Memorial Lecture, presented at the Annual Fall Technical
Conference sponsored by the Section on Physical and Engineering
Sciences of the American Statistical Association (ASA) and the
Chemical and Process Industries Division and the Statistics
Division of the American Society for Quality Control (ASQC).\\
\noindent (ii) The Youden Prize, awarded by the ASQC for the best expository paper
on statistical methods or philosophy that appeared in {\it
Technometrics} during the previous year.\\
\noindent (iii) The W.J. Youden Award in Interlaboratory Testing, given each year by
the ASA.

Youden's contributions to statistical methods include innovative
experiment designs, elegant procedures for displaying the results
of interlaboratory comparisons of measurement and test methods, and
a stream of techniques tailored for use to improve the quality of
scientific and engineering measurements.  He was a pioneer in the
application of twentieth-century Fisherian small-sample methods to
the planning and analysis of experiments in the physical sciences.
Following a brief outline of Youden's professional career, we
describe a few highlights.

From 1924 to 1948 he was on the staff of the Boyce Thompson
Institute for Plant Research in Yonkers, New York.  In about 1928
he and Frank Wilcoxon (q.v.) began using 
{\it Statistical Methods for Research Workers} by
R.A. Fisher (q.v.), and soon began contributing to statistical science. 
Youden
took leave during the academic year 1937-38 to work with Fisher at
the Galton Laboratory, University College, London. 
During 1942-45, he served as an operations analyst with the
U.S. Army Air Corps. 

From 1948 until his retirement in 1965, Youden was a senior staff
member of the Applied Mathematics Division at the National Bureau
of Standards (NBS) in Washington, D.C.; he continued this
affiliation as a Guest Researcher after his retirement.  At the
NBS, the U.S. national laboratory for physical measurement
standards, Youden produced more experiment designs, developed
interlaboratory testing procedures and his ``ruggedness" test,
wrote {\it Statistical Methods for Chemists} (Youden, 1951) and
other books, and from 1954 through 1959 published 36 columns under
the title ``Statistical Design" in {\it Industrial and Engineering
Chemistry}.

More complete biographical accounts are given in (Eisenhart and
Rosenblatt, 1972), (Eisenhart, 1976), (Ku, 1978), (Cornell, 1992),
and in a special issue of the {\it Journal of Quality Technology
(JQT)} dedicated to Youden (Lasater, 1972).  The {\it JQT} issue
contains a nearly complete bibliography of Youden's publications,
reprints of several of his papers and other materials, and a
``Summary and Index for `Statistical Design'" compiled by Mary G.
Natrella that describes his columns in {\it Industrial and
Engineering Chemistry}.  Eisenhart (1976) provides the definitive
scholarly account and completes the bibliography.

Youden was often heard telling a ``client" in consultation, or an
audience at one of this well-attended lectures, that he was a
``chemist", implying that he was really not a statistician.
Nevertheless, while he may have been all chemist for his first few
years at Boyce Thompson, the seed of his transformation to
statistician was planted early when he obtained a copy of the first
edition of Fisher's {\it Statistical Methods for Research Workers},
and seized the opportunity to apply the methods in experiments in
the field and in the greenhouse.  Evidence of this began to appear
in his publications in 1931.

The paper 
Youden (1937; reprinted in Lasater, 1972)
was the first in which he introduced new experiment designs.  The
new class of rectangular designs, termed ``Youden Squares" by
Fisher and Yates in the first edition, 1938, of their book of tables,
was found immediately to be of broad
utility in biological and medical research generally, and to be of
great value in scientific and engineering experimentation connected
with research and development.

The description of Youden's work as operations analyst during World
War II (Miser 1992) was entitled ``Craft in Operations Research",
but could as well be called ``craft in applied statistics".  Youden
directed groups of civilian scientists seeking to understand and
improve bombing accuracy, first in Britain and later in the Pacific
area, and was awarded the Medal of Freedom in 1946.  According to
Miser, stories are legion among the members of the Operations
Research Group of the Eight Bomber Command in England about
Yourden's exceptional skills in the invention of novel, and
adaption of standard, tools of experiment design and analysis, and
his gifts in divining the best way (officially or unofficially) to
get people to adopt his suggestions.  Miser's account is summarized
in a series of nine ``lessons", for example, ``When timely results
are important, simple forms of analysis can be useful", and ``It is
worth a great deal to shape one's explanatory theory into a form in
which it speaks clearly, easily, and forcefully to operational
people".  Youden's expository and persuasive skills are a recurrent
theme in any account of his work.

In 1948, Youden accepted Churchill Eisenhart's invitation to join
the newly established Statistical Engineering unit at the National
Bureau of Standards.  At the NBS, Youden was one of the first to
recognize and to capitalize on important differences between
experimentation in biological and agricultural sciences on the one
hand and in the physical sciences on the other.  Of paramount
importance, he noted, is the difference in the magnitude of the
error of measurement in the two areas.

Exploiting the precision of physical measurements, and responding
to the challenges presented by practical aspects of experimental
work, Youden developed several new kinds of designs.  One group,
``chain block designs", took advantage of special circumstances of
spectographic determinations of chemical elements carried out by
comparing spectrum lines recorded on photographic plates (Youden
and Connor, 1953). Experiments involving pairs of measurements
(blocks of size two) arose in the NBS thermometer, meter-bar, and
radium-standards programs.  This led to the development of
``calibration designs" where only differences (or ratios) are
observed for readings on two objects in blocks of size two (Youden
and Connor, 1954).  With J.S. Hunter, Youden developed ``partially
replicated Latin squares" to check whether the usual requirements
for a Latin square design have been met (Youden and Hunter, 1955).

The high degree of precision with which physical scientists can
repeat their measurements, with the same instrumentation set-up and
within a short period of time, sometimes lures them into claiming
an unwarranted confidence in their results and neglecting the
vagaries of other components of error such as day-to-day variation,
differences among nominally idential instruments and standards, and
possible systematic errors that are not obvious {\it a priori}.
Youden spared no effort in his lectures and writings to impress
upon his audiences that a realistic estimate of experimental error
could be obtained only through ``hidden replication", that is, that
a measure of precision should not be calculated from a series of
straightforward repetitions, but from discrepancies between the
measured values and the corresponding adjusted values derived under
conditions specified by a careful design.  In searching for
unsuspected sources of systematic errors, he advised the
experimenter, contrary to the time-honoured tradition of ``varying
one factor at a time", to a vary several factors at a time by
proper planning, such that the effect of each factor can be
measured with better precision than in the traditional way while
using the same number of measurements (Youden, 1961).  This 1961
paper introduced the ``ruggedness test", for investigating the
sensitivity of a method of measurement with respect to recognized
sources of systematic error and changes of conditions likely to be
encountered in practice.

By his publications and by his examples, Youden contributed
significantly to the achievement of objectivity in experimentation
and in the setting of more exacting standards for drawing
scientific conclusions.  His last major address, as retiring
President of the Philosophical Society of Washington in 1968, was
devoted to exposition of schemes for incorporating investigations
of systematic errors into experimental determinations of
fundamental physical constants.  The plea for explicit efforts by
scientists to accumulate objective evidence for the description of
the precision and accuracy of their work was entitled ``Enduring
Values" (Youden, 1972).

A significant fraction of NBS work is related to the development
and interlaboratory comparison of measurement and testing
procedures.  The ``Youden plot" procedure was designed to provide
simple but forceful interpretation of the results obtained in
several laboratories ostensibly using the same test method (Youden,
1959; reprinted in Lasater, 1972).

Youden proposed that each laboratory make determinations on two
specimens, chosen to have slightly different values of the quantity
to be measured, avoiding the possibility that systematic
differences between laboratories might be different at different
magnitudes of the measurand (a phenomenon called ``interaction" by
statisticians).  The Youden plot displays one point for each
laboratory, the value for the first specimen plotted against that
for the second.  If the laboratories differ only because of small
measurement errors, the points will fall within a roughly circular
area.  As is more often the case, however, the systematic
differences between laboratories cause the points to spread out
along a line with 45-degree slope so that laboratories that tend to
obtain low values and those that tend to obtain high values are
easily identified.  This procedure is widely used in programs for
proficiency testing of laboratories.

Youden had a talent for reducing a complicated idea to its
essentials and then expressing the idea through simple language. He
worked hard at it.  He was highly successful in convincing his
audience, specialists in other fields, of the reasonableness and
usefulness of a statistical idea, omitting all unnecessary details,
formulas, and statistical terms.  For example, in his book for high
school students, {\it Experimentation and Measurement} (Youden,
1962), the word ``statistics" does not appear once!  But the book
is about the use of statistical design and analysis in physical
experiments that can be performed readily by students.
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\noindent{\bf References}

\noindent{\it Selected works of Youden}:

\noindent (1937). Use of incomplete block replications in
estimating tobacco-mosaic virus. {\it Contributions from Boyce
Thompson Institute}, {\bf 9}, 50-57.

\noindent (1951). {\it Statistical Methods for Chemists}.
John Wiley and Sons, New York, N.Y., 126 pages.

\noindent (1953). The chain block design (with W.S. Connor). {\it Biometrics},
{\bf 9}, 127-140.

\noindent (1954). New experimental designs for paired observations
(with W.S. Connor). {\it J. Res. Nat. Bur. Standards}, {\bf 53}, 
191-196.

\noindent (1955). Partially replicated Latin squares (with J.S. Hunter).
{\it Biometrics}, {\bf 11}, 399-405.

\noindent (1959). Graphical diagnosis of interlaboratory test results.
{\it Industrial Quality Control}, {\bf 15}, No.11, 24-28.

\noindent (1961). Systematic errors in physical constants. {\it Physics Today},
{\bf 14}, No.9, 32-42.

\noindent (1962). {\it Experimentation and Measurement}. Vistas of Science
Series, National Science Teachers Association, Washington, D.C.,
128 pages.  Reprinted by the National Bureau of Standards as NBS
Special Publication 672, 1984.

\noindent (1972). Enduring values.  {\it Technometrics}, {\bf 14}, 1-11.
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\noindent{\it Biography and bibliography of Youden}:

\noindent Eisenhart, Churchill, and Joan R. Rosenblatt (1972). W.J. Youden, 1900-1971.
{\it Annals of Mathematical Statistics}, {\bf 43}, 1035-1040.

\noindent Lasater, H.A. (ed.) (1972). {\it Journal of Quality Technology}, {\bf 4},
1-67.

\noindent Eisenhart, Churchill (1976). William John Youden. {\it Dictionary of Scientific 
Biography},
Charles C. Gillispie, ed., Scribner's, New York, Vol.14, pp.
552-557.

\noindent Ku, Harry H. (1978). W.J. Youden. {\it International Encyclopedia of Statistics}
(W.H. Kruskal and J.M. Tanur, eds.), The Free Press, New York,
N.Y., pp.1257-1261.

\noindent Cornell, John A. (1992). W.J. Youden - The man and his methodology.
{\it ASQC Statistics Division Newsletter}, {\bf 13}, No.2, 9-18.

\noindent Miser, Hugh J. (1992). Craft in operations research.
{\it Operations Research}, {\bf 40}, 633-639.
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\hfill{Harry H. Ku and Joan R. Rosenblatt}


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