Normal, Gamma and Uniform distributions are the probabilistic
distributions used in this study. The Normal distribution
is considered because this is the theoretical assumption.
Gamma and Uniform distributions are considered to analyze
the impact on the various estimators of the process capability
index when alternative distributions are taken into account.
Finally, we considered off-center processes. In this situation,
the specification limits are selected such that Cpk ¼ f1; 1:5g.