Food and Drug Administration Commissioner Stephen Hahn conceded Monday night that he overstated the results of using convalescent plasma on coronavirus patients. His mea culpa came after scientists publicly excoriated him for saying the treatment saved 35 out of 100 people—after he mixed up two statistical concepts: absolute risk reduction and relative risk reduction. “The criticism is entirely justified,” Hahn said on Twitter. On Sunday night, the eve of the Republican National Convention, President Trump and the FDA announced an emergency-use authorization for the plasma, which is collected from people who have recovered from COVID-19 and have antibodies. Hahn denied that politics played a role in the authorization. “We at FDA do not permit politics to enter into our scientific decisions. This happens to be a political season but FDA will remain data driven,” he tweeted.