The number of people who buy two particular brands in a given time period does not depend on the brands as such but only on the numbers of people who buy each brand and on a general constant. The constant varies by product-field and by the length of the analysis-period, the correlation between buying any two brands being positive in relatively long periods and negative for shorter periods.
Author: Andrew S. C. Ehrenberg
June 15, 1987
Catalogue: ESOMAR Congress 1966
Author: Gerald J. Goodhardt
September 1, 1966
- This could also be of interest