How do you know that is good?

This is a question that I know many of you would have in your mind but none of you would have the answer to. When people do coffee maker ratings, how do you justify if the ratings that he gave is good? Or, how would you say that the ratings is accurate? I mean that person is sure to have biaseness, and he or she is sure to have his or her likes and dislikes right? Personally, after a few incidents I have stopped trusting these reviews. I do not think that they are purposefully trying to misled people, it is just that one man’s food might be another man’s poison sort of theory.