Abdul Has Volunteered to Participate in an Experiment Evaluating the Effectiveness

Multiple Choice

Abdul has volunteered to participate in an experiment evaluating the effectiveness of aspirin.Neither he nor the experimenters know whether the pills he takes during the experiment contain aspirin or are merely placebos.The investigators are apparently making use of

A) naturalistic observation.
B) a confounding variable.
C) the double-blind procedure.
D) random sampling.