Phil is a participant in a study designed to examine the effects of taking a dietary supplement on muscle tissue development. phil suspects he is in the experimental group, because he is certain his muscles are bigger and stronger as a result of taking the product supplied by the researchers. when the study is completed, phil learns that he did not receive the dietary supplement. phil thinks the researchers made a mistake—he is certain his muscle mass increased while he took the supplement. according to this information, phil's belief that his physical condition improved while he participated in the study is an example of .