the P-value and power are relative to the statistical method used for the analysis and not only to the sample size. Imposing stringent conditions on the significance of individual tests has become the popular approach to control the global significance of multiple tests. This number is related to the so called “family-wise error rate” that represents the probability of one or more type I errors in testing multiple hypotheses. The rationale is that, if the standard threshold α is adopted to accept a significant association when testing one single hypothesis, then the probability of one or more type I errors in testing N hypotheses is given by the formula
