6.3 Does meditation reduce anxiety? An experiment that claimed to show that meditation reduces anxiety proceeded as follows. The experimenter interviewed the subjects and rated their level of anxiety. The subjects were then randomly assigned to two groups. The experimenter taught one group how to meditate, and they meditated daily for a month. The other group was simply encouraged to relax more. At the end of the month, the experimenter interviewed all the subjects again and rated their anxiety level. The meditation group had a greater decrease in anxiety than the group told to relax more. These results might be biased because
(a) subjects should have been blinded to what treatment they received.
(b) the anxiety ratings at the end of the experiment should have been performed by someone blinded to which treatment a subject received.
(c) this is not a matched pairs design.
(d) the experimenter failed to use proper blocking.