In order to ensure that marketing campaigns are actually effective in their goals of attracting and retaining customers, it’s not enough to rely on primitive measures like click rates. Instead, every marketing campaign should be treated like a marketing experiment. When sending a promotion to a chosen market segment, set aside a small part of the population as a control, so you can compare the revenue from the control customers to the customers receiving the promotion. Then you’ll have a much better idea what influence the promotion had on customer behavior.

Read the full article here:
How to build a scientific approach to customer marketing – GigaOM