The way a researcher tells someone they were chosen for a study can change the study’s result before the treatment even begins.
We treat Randomized Controlled Trials as neutral 'gold standards,' assuming the selection process doesn't affect behavior. This study shows that subjects act differently if they think they were picked by a public lottery versus a private computer, meaning the 'neutral' design of an experiment is actually a hidden variable that can invalidate the findings.
RCTs, Awareness, and Assignment Effects
SSRN · 6469559
Randomized Controlled Trials (RCTs) are the gold standard for evaluating the effects of interventions because they rely on simple assumptions. Their validity also depends on an implicit assumption: that the research process itself, including how participants are assigned, does not affect outcomes. In this paper, I challenge this assumption by showing that outcomes can depend on the subject's knowledge of the study, their treatment status, and the assignment mechanism. I design a field experiment