Controlled experiments are those in which groups are separated into control and experimental. Neither group knows what they are receiving, so they may or may not be receiving a sugar pill or something else. The control group is essential for comparisons -- what happens in the control group often determines how the experimental data is interpreted (Scientific Control Group, 2008).

A double blind experiment is one in which some of the participants are prevented from knowing certain information about the study that might lead to bias (conscious or subconscious) thus skewing the results. Blinding can also be imposed on researchers, subjects, funders, or any combination in which one wishes to protect the data integrity. In the use of new drugs, blinded experiments are necessary because a patient might feel better if they think they are receiving a powerful new medicine -- the placebo effect. It is impossible, however, to double...
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