Which of the following is an example of a blind study?
A) Subjects are assigned to either the experimental or control condition by the experimenter, and are not told which group they have been assigned to.
B) Subjects are assigned to either the experimental or control condition based on their personal preference, and are told to write which group they have chosen on the consent form without notifying the experimenter.
C) Subjects are assigned to either the experimental or control condition based on their personal preference, and report their decision directly to the experimenter.
D) Subjects are assigned to either the experimental or control condition at random by an individual other than the experimenter.
Answer: A