Haphazard sampling is a strategy that is almost guaranteed to introduce bias into your study. It should be avoided at all costs. A typical haphazard strategy uses a "man-on-the-street" technique to recruit those who wander by or selects a sampling frame that does not accurately reflect the population.

The most famous haphazard survey was the one conducted by the Literary Digest to predict the winner of the 1936 presidential election. Participants were recruited from telephone books and automobile registration lists. The poll predicted that Landon would beat Roosevelt by a landslide. We now recognize that those who owned automobiles and could afford telephones during the depression era were more likely to vote Republican.