  We study the sensitivity to the CP/T-violation search in the presence of
ambiguities of the theoretical parameters. Three generations of neutrinos are
considered. The parameters whose ambiguities are considered are the differences
of the squared masses, the mixing angles, and the density of matter.
  We first consider the statistics that are sensitive to the genuine
CP-violation effect originating from the imaginary coupling. No ambiguity of
the parameters is considered in this part. It is argued that the widely-adopted
usual statistics are not necessarily sensitive to the genuine CP-violation
effect. Two statistics that are sensitive to the imaginary coupling are
proposed. The qualitative difference between these statistics and the usual one
are discussed.
  Next we proceed to the case where the ambiguity of the parameters is present.
The sensitivity of the CP-violation search is greatly spoiled when the baseline
length is longer than about one thousand kilometers, which turns out to be due
to the ambiguity of the matter effect. Thus the CP-violation search by use of
CP conjugate channels turns out to require a low energy neutrino and short
baseline length. It is also shown that such a loss of sensitivity is avoided by
using T-conjugate oscillation channels.
