Tiny effect is among the issues of our time ‘that science has taken a turn towards darkness.’ 1 In the Catheter Ablation for Atrial Fibrillation with Heart Failure (CASTLE-AF) trial,2 the primary end point was death or hospitalisation for worsening heart failure. The authors concluded that: ‘after a median follow-up of 37.8 months, the primary composite end point occurred in significantly fewer patients in the ablation group than in the medical therapy group (51 patients (28.5%) vs 82 patients (44.6%); difference 16.1% (CI) 5%–25%. HR 0.62; 95% CI 0.43 to 0.87; p=0.007).’ That was statistically significant. Although the inferential …