interval to estimate advertising carryover. The literature assumes that (1) the optimal data interval is the interpurchase time …

's purchases follow a Poisson process (hence exponential interpurchase time), and purchase rates are distributed gamma across … the number of purchases or the interpurchase time data to estimate this heterogeneity, we suggest that number of purchases … for models using number of purchases data (e.g. NBD), it may be very misleading for models using interpurchase time data …