One third of people will agree with an answer they can see is wrong

Solomon Asch asked participants to match line lengths — an unambiguous, easy task. But when several actors in the room confidently gave the same wrong answer first, real participants conformed to it about a third of the time on average, and three in four conformed at least once across the trials. Correcting your own eyes felt riskier than looking foolish alone.

— Solomon Asch, Asch conformity experiments — Swarthmore College study, 1951