You can do an incremental response model (a.k.a. net lift model) for the data with campains when you only sent the offer to certain customers. A paper that uses direct marketing as an example: Net Lift Model for Effective Direct Marketing Campaigns at 1800flowers.com A paper that goes a little deeper into theroy and an example: Incremental Response Modeling Using SAS® Enterprise Miner™ I hope this helps! -Miguel
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