Superiority vs. equivalence/non-inferiority: study design and meeting abstracts

Excerpt

In a superiority study, the authors hypothesize that one study is superior to another — i.e. A is superior to B. When there is a statistically significant difference between the studies (usually defined as P<0.05), superiority of one study has been demonstrated. When there is not a statistically significant difference between the studies (P≥0.05), this does not necessarily indicate that the two studies are equivalent (A is equivalent to B or A is non-inferior to B) or that the opposite result is true (B is superior to A). Rather, it simply indicates that superiority was not demonstrated. Failure to demonstrate superiority could indicate one of two things: (1) the result is correct (A is truly not superior to B) and/or (2) the study lacked sufficient power/sample size (we don’t know whether A is superior to B). …