Type I error rate inflation occurs when a single hypothesis is
tested indirectly using inferences about two or more (i.e., a family of)
sub-hypotheses. In such situation, the probability of type I error (i.e., the
probability of incorrectly rejecting the null hypothesis) of the single,
familywise, hypothesis is higher than the lowest, testwise, probabilities. As
a consequence, the rejection of null hypothesis for one or more individual
tests does not warrant that the correct decision (whether to reject the the
null hypothesis on a familywise basis) was taken properly. This function
allows to obtain correct, familywise, alpha thresholds in the context of
multiple testing. It is base on the Sidak inegality.