Imagine that a group of researchers designed a study to test the effectiveness of subliminal-message weight-loss tapes.Half the participants receive real tapes,and half receive similar tapes with the subliminal messages removed.The experimenter keeps track of which participant is in which group.All the participants are told that their tapes contain subliminal messages.What type of study is this

A)  anecdotal research 
B)  case study 
C)  double-blind procedure 
D)  single-blind study

Double-Blind Procedure

An experimental method where neither the participants nor the experimenters know who is receiving a particular treatment, to prevent bias.

Subliminal Message

Messages that are designed to pass below the normal limits of perception, intended to influence the subconscious mind without conscious awareness.

Effectiveness

Effectiveness refers to the degree to which a process, action, or intervention achieves its intended outcome or goals under normal or real-world conditions.