Secondary endpoints can be validly analyzed, even if the primary endpoint does not provide clear statistical significance.

Response variables from clinical trials are often divided into those considered primary and those considered secondary to the purposes of the study. If the difference between treatment groups on primary outcomes is not significant, the interpretation of significant differences in secondary response variables may be difficult because of multiple comparisons. It is proposed that the comparison on the primary outcome use a significance level of alpha and that the secondary endpoints be evaluated using a significance level alpha/(k + 1), where k is the number of secondary outcomes to be evaluated. Examples from recently completed clinical trials illustrate the use of this rule.