This can provide data on the extent to which people are changing their behavior due to simply being in the experiment. Yet this is not always feasible to do and sometimes it is hard to distinguish the placebo effect from the actual treatment effects, especially with counseling and other treatments that resemble the effects of people sensing someone is paying increased attention to them as in an experiment. Given the problems of generalizability, sometimes cross-sectional studies, l ike surveys of large probability samples, are preferred. Post-hoc controlling through multivariate analysis of the survey data, based on extended survey questions on many different background factors, is used to try to approximate establishing the conditions for making causal inferences. Classic experiments of compared equivalent groups can be done in the field but field conditions of the real world of service delivery can complicate the process of ensuring a real experiment with equivalent groups, random assignment, and controls for threats to internal validity.
Field experiments present extra challenges.
Classic experiments are themselves not always feasible, especially where we want to study actual programs, services, treatments, etc., as they are being administered in the real world. This is especially the case when it is difficult or impossible to randomly assign clients and create equivalent groups. This is especially the case where there are ethical issues regarding deciding who should or should not get access to a service. Here we turn to quasi-experimental designs. Given the limitations of experiments, triangulation to measure the same effect in multiple ways is advised.