The chief aim of probability sampling is to be able to select:

Recall that in one condition of the experiment conducted by stasser and titus (1985) about student council president candidates, all group members had access to the same information, and that in another condition, members had unique information that other group members didn't know. in the second (unshared information) condition, the group made a worse decision than in the first (shared information) condition. this occurred because groups seldom can agree on who is most expert. focus discussion on the information that all members know. often ignore dissenting opinions. avoid differences of opinion, given conformity pressures.