A(n) allows researchers to distinguish the specific effects of the independent variable from the possible effects of the experimenter and participants' expectations about it.

I believe the answer is: double-blind experiment

In double blind experiments, the subjects that receive the treatment is remained unknown by both the researchers and the subjects until the experiment is finished. The main purpose of double-blind experiment it eliminate the bias of perception that might exist among researchers.

experiments.

surveys.

questionnaires.

interviews.

case studies.

participant and non-participant observation.

observational trials.

studies using the delphi method.