Asch carried out a lab experiment with an independent groups design. In groups of 8 participants judged length of lines by saying out loud which comparison line matched. Each group contained only one real participant, the others were confederates. The real participant always went last or last but one, so that the others gave their answers first. Each participant did 18 trials. In 12 of these the confederates gave the wrong answer. There was also a control group where the participants judged the line length on their own.
In the control trials, participants gave the wrong answer 0.7% of the time. When the confederates gave the wrong answer participant conformed to the majority 37% of the time. 75% conformed at least once. Afterwards some participants said they didn't really believe in their answers, but didn't want to look different.
The control condition showed the task was easy to get right. However 37% were wrong on the trials where to confederates gave the wrong answer. They conformed to the majority and therefore this was a normative influence.