Prior to the experiment, Milgram solicited predictions from psychiatrists, college students and middle-class adults as to what percentage of the participants in the experiment would go the point of administering a "lethal shock" of 450 volts. The estimate from all groups was 0% to 3% (mean of 1.2%). As it turned out, a staggering 65% (24/40) of the participants administered "shocks" of up to 450 volts.
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I noticed a typo in the last sentence. 24/40 should be 26/40.