When Less Is More: Data and Power in Advertising Experiments
通过3百万用户的随机田野实验，发现网络展示广告使销售额提升3.6%，且仅用一半数据即可使估计精度提高31%，优于添加协变量的传统方法。
Yahoo! Research partnered with a nationwide retailer to study the effects of online display advertising on both online and in-store purchases. We use a randomized field experiment on 3 million Yahoo! users who are also past customers of the retailer. We find statistically significant evidence that the retailer ads increase sales 3.6% relative to the control group. We show that control ads boost measurement precision by identifying and removing the half of in-campaign sales data that are unaffected by the ads. Less data give us 31% more precision in our estimates—equivalent to increasing our sample to 5.3 million users. By contrast, we only improve precision by 5% when we include additional covariate data to reduce the residual variance in our experimental regression. The covariate-adjustment strategy disappoints despite exceptional consumer-level data including demographics, ad exposure levels, and two years’ worth of past purchase history. Data, as supplemental material, are available at http://dx.doi.org/10.1287/mksc.2016.0998 .