The assignment is done in such a way that neither the patients nor the physician evaluating the patients' responses knows who is getting which. At the end of the study, the codes are broken and the results tallied and analyzed. The ideas often come from a single founder and are then passed along with little change to successive generations of students as in the case of chiropractic or homeopathy. New treatments may sometimes be added by others, but the core theories are not challenged. Alternative medical treatments are often promoted through the use of anecdotal evidence and testimonials.
Anecdotal evidence consists of stories of how a treatment worked in individual cases.
Testimonials are statements from alleged satisfied customers. They may be fabricated or contributed by people with a financial interest in the product. Even when they are genuine they are often misleading. Typically only the best testimonials are selected out to present. Under the very best of circumstances they are still subject to the same sources of unintentional bias that plagued the trial of liver extract and vitamins mentioned above.