Herbert Robbins is widely recognized as one of the most creative and original mathematical
statisticians of our time. The purpose of this book is to reprint on the occasion of his
seventieth birthday some of his most outstanding research. In making selections for reprinting
we have tried to keep in mind three potential audiences: (1) the historian who would like to
know Robbins' seminal role in stimulating a substantial proportion of current research in
mathematical statistics (2) the novice who would like a readable conceptually oriented
introduction to these subjects and (3) the expert who would like to have useful reference
material in a single collection. In many cases the needs of the first two groups can be met
simulta neously. A distinguishing feature of Robbins' research is its daring originality which
literally creates new specialties for subsequent generations of statisticians to explore. Often
these seminal papers are also models of exposition serving to introduce thereader in the
simplest possible context to ideas that are important for contemporary research in the field.
An example is the paper of Robbins and Monro which initiated the subject of stochastic
approximation. We have also attempted to provide some useful guidance to the literature in
various subjects by supplying additional references particularly to books and survey articles
with some remarks about important developments in these areas.
