People and Cookies: Imperfect Treatment Assignment in Online Experiments - Meta Research | Meta ResearchPeople and Cookies: Imperfect Treatment Assignment in Online ExperimentsWWW 2016 Identifying the same internet user across devices or over time is often infeasible. This presents a problem for online experiments, as it precludes person-level randomization. Randomization must instead be done using imperfect proxies for people, like cookies, email addresses or device identifiers. Cookies present a u
