Before revision: Policy evaluation studies, which aim to assess the effect of an intervention, imply some statistical challenges:  real-world scenarios provide treatments which have not been assigned randomly and the analysis might be further complicated by the presence of interference between units.
After revision: Policy evaluation studies, which aim to assess the effect of an intervention, imply some statistical challenges: real-world settings treatments are not randomly assigned and the analysis might be further complicated by the presence of interference between units.