If there is one loud-mouth in your group who keeps repeating his opinion over and over again, can easily give the impression that this is the opinion of the whole group.
See this post for:
The study, carried out by Kimberlee Weaver and colleagues, found we can tell that three different people expressing the same opinion better represents the group than one person expressing the same opinion three times – but not by much.
In fact, if one person in a group repeats the same opinion three times, it has 90% of the effect of three different people in that group expressing the same opinion. When you think about it, that is strange. Indeed, I’m not sure I’d even believe it if I hadn’t already read many other psychology studies that point to the illogical and unreasonable ways our minds sometimes work.
See full article. You might think that intelligent people can easily make out that it’s just one person repeating his opinion, as opposed to the whole group. But you might be wrong. It is fascinating how easy it is to mislead intelligent people. Read my other posts in the psychology section for more examples of this kind of stuff.