Demand bias occurs when the purpose of the study is revealed to the respondents prior to the research taking place. This can influence not only the results of the study, but may impact the type of respondents that agree to participate in the research. This is most often a factor with consumer surveys, studies, and focus groups, where identifying information about the survey will influence the makeup of the pool of respondents.
For example, recruiting participants for a survey on smartphones that specifies the research is being done on behalf of “a major smartphone manufacturer” will surely skew the respondent pool makeup, as well as the survey results. This is a blatantly obvious example, but a less obvious scenario entails clueing in the respondent group through a poorly designed screening survey. Indeed, asking screening questions that only pertain to the subject you’re researching will provide clues as to which company, or type of company, may be sponsoring the research
How can you avoid demand bias? Obviously, keep the sponsor confidential, as well as the company type and industry. When respondents feel that they are being recruited by a specific brand or type of company, both promoters and detractors—rather than typical consumer—may be more likely to want to participate.
When gathering respondents, it is also advisable to include several questions about a variety of topics to obscure the goal of the research. For example, in our cell phone study example, it’s good practice to include screener questions about not only cell phone purchasing, but also about computer purchasing, insurance purchasing, and automobile purchasing. This serves two purposes: the variety of topics makes it more challenging for potential respondents to hone in on the true purpose of the study, and the data gathered at this stage may provide a screened pool for surveys or projects in the other subject areas covered in the screening process.
Demand bias is generally not an issue for experienced research firms, but it’s an important topic to keep in mind for companies that choose to hold their own focus groups or conduct their own customer surveys. By cloaking the true nature of the project, the respondents and responses to that project are likely to be more honest and untainted than if they know the parameters of the survey.