Correct contract bridge / by E.V. Shepard ; including the official Laws of contract bridge adopted by the Whist Club, New York, and by all the leading clubs in America.

140 CORRECT CONTRACT BRIDGE
An event averaging to occur only 20 times in 100
opportunities, if capable of duplication by a maximum of three suits or three hands, will be duplicated only 488,oo000 times in 1,000,000 cases, and
unduplicated 512,000 times Evidently an event
must appear more frequently than 20 times in 100 to
expect its duplication when discovered in your own
hand.
An event averaging to occur 21 times in 100
opportunities, if capable of being duplicated by any
or all of three hands (or suits) will be duplicated
by at least one of those hands (or suits), 506,961,
and unduplicatec 493,039, times in i,000,000 opportunities. Thus we establish as our minimum
limit for an event to probably be duplicated by at
least one of three possibilities, that such an event
must average to appear 21 times in ioo00 opportunities. This proven fact gives us the first of the three
Theorems that follow.
There are only three chances for duplication, because one of the four hands or four suits contains
the original. But a feature of a vertical distribution may be paralleled by a horizontal distribution
of any one of the four suits, permitting a lower
limit of symmetry for parallelism than for duplication.
An event or feature that has i6 in ioo00 chances
to appear, results in being paralleled 50,212,864
times in 100,000,000 opportunities, and being unparalleled 49,787,136 times; thus establishing the
limit of symmetry for parallelism-giving us
Theorem 2.