Controlled feedback and iteration. The results of a given round of responses are summarised and reported to the group, who are then asked to reassess their replies in light of the feedback. Formal group judgement . Anonymity is a restriction to combat the biasing effects of group pressure, dominant individuals, and the like, and assures, with formal group judgement, that the answer of every individual in the group is taken into account in the final group judgement. Iteration with feedback allows a certain amount of interchange among the members of the group but in a controlled manner.
Formal aggregation gives a well-defined group response.
And so on. The Delphi procedures are designed to meet the many concerns about group think, but they clearly needed validation. There are two routes to validation, experimental and theoretical. In an extensive series of experiments at the RAND Corporation and the University of California at Los Angeles, the effectiveness of the procedures, as well as many variations, was tested, using graduate students as subjects and 'almanac-type' questions where the subjects did not know the answers, but had some relevant knowledge. The experimenters could obtain the answers from reference sources.