LSD microdosing experiment: pair 20: placebo then active?

Created by gwern on 2013-03-10; known on 2013-03-11; judged right by gwern on 2013-03-10.

• gwern estimated 75% on 2013-03-10
• gwern on 2013-03-10
• gwern   judged this prediction right on 2013-03-10.