PANELS A specialized poll in which respondents are interviewed again and again as part of an ongoing study. Panels use the same respondents for two, three, four, or more interviews ( Johnson and Joslyn, 1986:111-112). The panel method was developed by the renowned sociologist Paul Lazarsfeld. His classic study of voting behavior, The Peoples Choice, ( 1944) is still a leading example of the technique. Lazarsfeld and his colleagues interviewed over six hundred people in Erie County, Ohio, once a month for six months. Respondents were asked about their voting intentions and the things that influenced their thinking about the upcoming election ( Williamson et al., 1982:130).
Today panels are widely used in consumer research, audience research, and political polling. They have one paramount advantage over other polls: panels monitor change in individuals from poll to poll. This allows researchers to find out who is changing, who is not, and why. By contrast, nonpanel polls allow only net change to be measured from one poll to the next. Knowing only net change may obscure enormous shifting back and forth of opinion between surveys ( Clark, 1976:20).
Of course, panels also have drawbacks. The most serious is the mortality problem--which is people dropping out of the panel. Mortality is a serious threat to the representativeness of panels, since people who drop out of panels are usually different than those who remain. The other problem with panels is their potential for reactivity; that is, respondents may become biased from repeated interviewing. This problem, known technically as the interaction effects of testing, can occur if respondents change simply because they have been interviewed. They may pay more attention to news, be more aware of issues, or think more about the matters on which they are questioned ( Babbie, 1973:64,65,43; Weisburg, Krosnick, and Bowen, 1989:133-134). See also CONDITIONING; DROPOUTS; LONGITUDINAL SURVEYS; TREND STUDIES.