I never thought Philip K. Dick will give us a good explanation of Quorum. Following is the original excerpt from “The Minority Report”:
The system of three precogs finds its genesis in the computers of the middle decades of this century. How are the results of an electronic computer checked? By feeding the data to a second computer of identical design. But two computers are not sufficient. If each computer arrived at a different answer it is impossible to tell a priori which is correct. The solution, based on a careful study of statistical method, is to utilize a third computer to check the results of the first two. In this manner, a so-called majority report is obtained. It can be assumed with fair probability that the agreement of two out of three computers indicates which of the alternative results is accurate. It would not be likely that two computers would arrive at identically incorrect solutions”
Reference: Philip K. Dick. The Minority Report. In: Selected Stories of Philip K. Dick. New York: Houghton Mifflin Harcourt, 2013. see this link
For all german speakers, I recommend this recently published anthology of Philip K. Dick’s well-known short stories.