A word on Bias
Our values, emotions, desires and experiences influence our decisions and can go both ways; positively and negatively. It is in our capacity to set these factors aside to achieve an open mind and enable ourselves to evaluate the information at hand.
Authority Testimonials are often seen in commercials and advertisements as proof of a products effectiveness. This can be linked to common mistake number one: we prefer stories to statistics. Be a smart consumer, conduct research. Verify as to what is this persons capacity to stand for this certain product. Is he an expert on the subject matter? Is he a licensed professional? Learn to ask smart questions and more importantly, learn how to get the answers to these questions.