Many authoritative advertisements include some type of scientific or survey evidence. Independent organizations, such as the American Medical Association, undertake a variety of product studies. Quoting the results gives an ad greater credibility. Survey results are less credible. Stating that four out of five dentists recommend a particular toothbrush or toothpaste is less effective, because the statement is too vague. When the American Medical Association states that an aspirin per day will reduce the risk of a second heart attack, however, the endorsement is highly credible. An aspirin company can take advantage of the finding by including it in their ads. The same is true when a magazine such as Consumer Reports ranks a particular brand as the best. Any scientific and independent source not paid by the advertising company makes an advertising claim more believable.