Also known as selection bias, an error in choosing participants for a scientific study such that the results are distorted.
Example: A famous example is a political telephone survey conducted during the Truman-Dewey presidential race. Survey results indicated that Dewey would win by a landslide, failing to account for the fact that telephones were expensive at the time and only owned by a small, wealthy fraction of the population — people who tended to support Dewey more than the average voter.
Some people who conduct studies might decide to make the research more convenient for them by staying within their neighborhood. Their neighborhood could be the poorest section of town or richest…either way, there is bound to be a bias. Generally speaking, people tend to spend time with those who are like-minded, so it is important that the researcher make a very strong effort to leave their comfort zone and get a more authentic reading.