  An inequality is deduced from Einstein's locality and a supplementary
assumption. This inequality defines an experiment which can actually be
performed with present technology to test local realism. Quantum mechanics
violate this inequality a factor of 1.5. In contrast, quantum mechanics
violates previous inequalities (for example, Clauser-Horne-Shimony-Holt
inequality of 1969, Freedman-Clauser inequality of 1972, Clauser-Horne
inequality of 1974) by a factor of $\sqrt 2$. Thus the magnitude of violation
of the inequality derived in this paper is approximately $20.7%$ larger than
the magnitude of violation of previous inequalities. This result can be
particularly important for the experimental test of locality.
