Most students, however, believe that probability sampling strategies are beyond their reach because of cost and time factors. In fact, some probability sampling strategies are very easily used in campus settings (Sampling Workshop). Nonprobability sampling can also result in a reasonable representation of the population but we must exercise care to avoid bias. Haphazard sampling is the strategy that can produce the greatest bias and should be avoided.

Haphazard samples are gathered with little thought about the characteristics of the sample and the types of biasing factors that might be introduced. The most common haphazard sample is gathered by students asking a favorite psychology professor if they can recruit participants from their class. While this strategy can result in a large and cooperative sample, it might also bias the results. Psychology students know psychological theories and may be familiar with your topic of research. They may be sophisticated about different strategies and can guess the hypothesis. Because of their interest in psychology, they may share characteristics such as sociability and empathy that are not as prevalent in the rest of the college population.