Superiority Trial
A clinical trial designed to show that a new treatment is better than the comparator (placebo or active control) by a statistically significant margin. Most pivotal peptide drug trials are superiority designs aiming to demonstrate a clear treatment benefit.
Technical Context
Superiority testing uses a two-sided hypothesis: H0 (null): treatment effect = 0 (no difference); H1 (alternative): treatment effect ≠ 0. The trial is powered (typically 80-90%) to detect a pre-specified minimum clinically important difference (MCID) at a significance level of α = 0.05 (two-sided). Sample size calculation depends on: expected effect size, variability (standard deviation) of the primary endpoint, desired power, significance level, and expected dropout rate. For weight management trials, semaglutide Phase III programmes were powered to detect superiority over placebo with co-primary endpoints (% weight change AND ≥5% weight loss proportion) — both must be statistically significant for the trial to succeed.