Regardless of the type of evidence a writer chooses to use, it should always be relevant, accurate, and sufficient. Relevant evidence is evidence that specifically applies to the argument being made. To argue that a particular car is superior from a dependability standpoint, bringing in evidence about its maintenance record would be relevant, but talking about its hand-tooled leather seats would not. Generally, good writers do not leave the relevance of a piece of evidence to the reader’s imagination; they explicitly spell out what the relationship is between an example and the argument at hand.

Presenting accurate information means taking care to quote sources correctly without misrepresenting what the sources are saying or taking the information out of context. One way to ensure that you have accurate evidence is to get it from a credible source. Think carefully about the bias any source might have. Is it partisan or backed financially by a company or an industry group? Even statistical data can be inaccurate if it is from a source that has gathered the data in a way that fits its own agenda. Accuracy can also be a matter of the audience’s perception. You should choose sources that they will find credible. If you want accurate dependability information about a car, some reliable sources might be a reputable mechanic, a magazine reviewer who has compared the car’s performance to other similar cars, or simply someone who has owned the car for a long time.

Finally, you should include a sufficient amount of evidence to support your thesis. If you based your entire argument about the car’s dependability on an interview with a single mechanic, that would not be persuasive. A mechanic only sees the cars that break down, so perhaps his viewpoint is overly negative.