Abstract: Techniques for generating unbiased estimates of causal effects in online experiments are provided. In one technique, campaign data is received that includes a first set of targeting criteria and a second set of targeting criteria. An online experiment is established that comprises a content delivery campaign that is associated with a treatment group and a control group. Afterward, a content request is received and a first entity that initiated the content request is identified. In response to determining that the first entity is targeted by the campaign based on the first set of targeting criteria, the first entity is randomly assigned to the control group. In responses to second content request, a second entity is identified. In response to determining that the second entity is targeted by the campaign based on the first set of targeting criteria, the second entity is randomly assigned to the treatment group.