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.

68 CORRECT CONTRACT BRIDGE

other player doubles, each of the two remaining
players temporarily is credited with having one-half
the honor strength not required by the bidder and
the doubler; in addition, the doubler's partner
averages to have I Y2 tricks in low cards of his best
suit. An opening bid of I-odd in any suit, or of 3 -odd in a major suit or 4-odd in a minor suit, require
so little side strength in honors that on an average
the partner of one making an informatory double
has at least three tricks total, requiring the informatory doubler to furnish the balance of the tricks
needed to fulfill the contract forced from the
doubler's partner. Informatory doubles that adhere to these basic facts are sound and must average
to produce favorable results.
An analytical mind requires no set rules for making a sound informatory double of any opening bid.
Suppose that you contemplate making an informatory double of I-No Trump. If that bid has been
made at your left it cannot go game except from an
adverse score of at least 65 points; any lower score
does not justify a double unless you believe that
your side can go game, or unless your values make
it probable that you can score something safely and
that you can collect a substantial penalty in case
opponents try to outbid you. In case the i-No
Trump is made at your right you face an entirely
different situation from when the declaration occurs
at your left. An opening bid of I-No Trump rarely
shows more than 6 honor tricks; suppose that you
hold 5 honor tricks and have a hand well able to
support any response by your partner, or else you