10 Types of Study Bias

Question-Order bias
A researcher asks two women for their views concerning the creation of a state health service in England in the 1940s. The order questions are asked can influence the answers received. Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images

The order that questions are asked in a survey or study can influence the answers that are given. That's because the human brain has a tendency to organize information into patterns. The earlier questions — in particular, the ones that come just before a particular query — may provide information that subjects use as context in formulating their subsequent answers, or affect their thoughts, feelings and attitudes. That effect is called priming [sources: Pew, Sarniak].

Pew Research gave this example from a December 2008 poll: "When people were asked 'All in all, are you satisfied or dissatisfied with the way things are going in this country today?' immediately after having been asked 'Do you approve or disapprove of the way George W. Bush is handling his job as president?'; 88 percent said they were dissatisfied, compared with only 78 percent without the context of the prior question."

Another example of the question-order bias effect comes from the General Social Survey, a major long-term study of American attitudes. In 1984, GSS participants were asked to identify the three most important qualities for a child to have, and given a card with a list of qualities. When "honest" was high on the list, it was picked by 66 percent of respondents. But when it came near the end, only 48 percent of people picked it as one of their top three. A similar pattern was seen with other qualities [source: Henning].