The negative exponential

Date of publication: June 15, 1988

Author: Joel D. Levy


This paper shows how RBL responded to marketing managements' changed needs by adapting mini-testing methodology to reduce the time necessary for testing in a way which preserved the extended observation of the repeat buying behaviour of panellists as the basis for forecasting stable repeat purchasing rates. The standard set for the new methodology in terms of its success was the ability to provide predictions comparable with standard 20-24 week Mini-Test Market estimates of volume potential. This paper describes how the examination of Mini-Test Market data was used to build a model using the negative exponential, and how this model was shown to be capable of predicting the long term repeat purchase rate of FMCG products on the basis of 12 elapsed weeks observation of repeat purchasing data comparable with estimates achieved in the standard 20-24 week Mini-Test.

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