Medical researchers often test medicines on patients who have given informed consent for the tests. The researchers divide the patients into two groups. One group is given the medicine. The second group is given a harmless substitute such as sugar pills. Neither the patients nor the researchers know which patients have received the medicine and which have received the substitute.

The question is incomplete, below is the completed question:

Medical researchers often test medicines on patients who have given informed consent for the tests. The researchers divide the patients into two groups. One group is given the medicine. The second group is given a harmless substitute such as sugar pills. Neither the patients nor the researchers know which patients have received the medicine and which have received the substitute.  What is the purpose of such a procedure?

to increase accuracy

to increase precision

to decrease bias

to decrease patient safety

The correct answer is:

to decrease bias

Explanation:

This kind of experimental setup where a group of participant is given a non-medical treatment is known as a double-blinded placebo experiment. The principle of the use of a placebo is to reduce biases. Biases are influences that may affect the result of an experiment that does not arise from the effect of the treatment itself, but from some external factor. The researcher and the subject do not know which treatment is a 'sham', and which treatment is the real treatment, it helps to make approach neutral and rules out any effect of manipulations that may affect the result as a result of such knowledge.

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