In order to give a more complete description of an actual experiment on EPR paradox, the upper limits for Bell and Clauser-Horn-Shimony-Holt inequalities are deduced in the case of three-valued observables. This limit results a function of the supplementary assumptions. The different cases of "random no-detection processes' and "parameter-independent selection" are discussed. A new stronger limit η= 0.811 is deduced for the quantum detection efficiency in order to perform a "loophole-free" experiment.