Multiple Presentations - Part 2
By Michel Adar on Dec 12, 2011
In the first part of this series we explored the problem of predicting likelihood with multiple presentations of the same content. In this entry we will explore a few more options.
Modeling Options (continued)
With presentation caps a person decides on a threshold which is the maximum number of times a specific content is to be used with any given person. For example, "this offer should not be presented more than 5 times to the same customer."
This scheme avoids the problem of wasting presentations in the long tail, but as any arbitrary threshold, it is not optimal. If the number is too large, then there are going to be wasted presentations and if it is too small, then the effort will quit too early, leaving potential customers "unimpressed."
An additional problem with this scheme stems from the fact that there may be a change inthe situation of the customer. That is, maybe this offer was not relevant a month ago, but now, with changed circumstances it may be relevant. A way to solve this problem is to set an expiration date for the cap.
In summary, for each choice two numbers are given, the maximum number of times to present the same choice to the same person, and the number of days after which the count is reset.
Purple line represents the believed likelihood before the cap is reached. Yellow marked area represents overestimation and red underestimation of the likelihood.
It is also clear that if the cap is too low then the untapped potential - the red area - grows tremendously. Conversely, if the cap is too large then the wasted presentations - the yellow area - become more and more significant. Therefore, quite literaly, using a presentation cap is like fitting a square peg in a round hole.
A further problem with this approach is one of modeling. Should you train the model with each presentation or only when the cap is reached?
In the next installment we will explore a possible better approach.