When researchers are interested in detailed information about purchasing behaviour or insight into certain leisure activities, they will often resort to panels of consumers. A panel will allow the researcher to track behaviour using the same sample over time. This type of longitudinal research provides more reliable results on changes that occur as a result of life cycle, social or professional status, attitudes and opinions. By working with the same panel members, intentions can be checked against action, one of the more problematic challenges that researchers face when studying planned purchases or intentions to engage in certain behaviour (e.g. going on trips, visiting certain sites, participating in sports, etc.).
But looking at trends is not the only use for panels. They can also provide invaluable insight into product acceptance prior to the launch of a new product or service, or a change in packaging, for instance. Panels, whether formally established or tracked informally through common behaviour (e.g. membership in a club, purchase of a specific product, use of a fidelity card, etc.), can also be used to study the reaction to potential or actual events, the use of promotional materials, or the search for information.
Compared to the depth interview and the focus group, a panel is less likely to exaggerate the frequency of a behaviour or purchase decision, or their brand loyalty. Although panels only require sampling once, maintaining the panel can be both time-consuming and relatively costly as attrition and hence finding replacements can be quite high. In order to allow researchers to obtain more detailed follow-up information from panel members, they are usually paid for their services. At the same time, this can introduce a bias into the panel, since the financial incentive will be more or less important depending on the panelists economic status.
Possibly one of the more interesting advantages of panels is that they can provide significant insight into non-response as well as non-participation or decisions not to purchase a given product.
Related Readings (link to Library. Lapage, W.F., Ch. 40 in Ritchie and Goeldner; Kumar, V., Aaker, D.A. & Day, G.S. (1999). Essentials of Marketing Research. New York: John Wiley & Sons, Inc.)