Does purchase history increase the validity of consumer panels? A case study
In a random sampling of consumers, it is not unusual to have a proportion of the panellists who are neither users or purchasers of the product. This means that “liking” responses to products are not informed by either context or experience. This reduces the validity of the test. When we consider that choice reflects the ability to detect a difference, in general population consumer difference tests the accepted proportion of differentiators (Pd) is only 30%. To increase the validity of consumer tests, particularly in the case of product matching, it is important to gather the responses of actual product consumers and if possible, heavy users.
In standard recruitment, consumers are asked to identify their own purchase and usage behaviour. It is commonly recognized that consumers will answer these questions based upon their recollection or response to the desire to participate in the test. In short, consumers lie; this compromises the quality of the data collected.
By recruiting consumers on the basis of purchase history, it is possible to increase the proportion of consumers in the panel who are real customers. The information can be gained from actual purchase history. The usefulness of this information was tested in two ways. Previous studies were examined to determine which of the consumers who were part of the test were verified as regular purchasers. Non-users and regular purchasers were grouped and compared on the basis of their historic data. The range of products evaluated by about 100 consumers each were; Bath Essence, Deodorant, Laundry Tablets and Food Wrap. Similar conclusions and power of the test were obtained with 20 to 35% fewer regular customers. A verification study with Tesco Home Panels using two groups of consumers was performed on a selected non-food product (Laundry Tablets). One group was composed of proven product purchasers. The second group was made up of proven non-purchasers. Their liking results were analyzed for both mean results and variance. Power tests performed on random subsets of the data demonstrated that smaller panels of well selected consumers reliably deliver the same outcome.
Findlay, C.J., Wilson, H., Spears, M., Cowen, S., & Castura, J.C. (2009). Does purchase history increase the validity of consumer panels? A case study. In: 8th Pangborn Sensory Science Symposium. July 26-30, Florence, Italy.