  The opening book is an important component of a chess engine, and thus
computer chess programmers have been developing automated methods to improve
the quality of their books. For chess, which has a very rich opening theory,
large databases of high-quality games can be used as the basis of an opening
book, from which statistics relating to move choices from given positions can
be collected. In order to find out whether the opening books used by modern
chess engines in machine versus machine competitions are ``comparable'' to
those used by chess players in human versus human competitions, we carried out
analysis on 26 test positions using statistics from two opening books one
compiled from humans' games and the other from machines' games. Our analysis
using several nonparametric measures, shows that, overall, there is a strong
association between humans' and machines' choices of opening moves when using a
book to guide their choices.
