Examples used are fairly typical instances, not extreme or isolated cases. Or evidence is 'common knowledge', accepted as true by most educated readers. Evidence may also be a source of non-logical appeal when the evidence not ony supports a claim factually, but also appeals in some way to the audience's emotions, needs, or values. Examples may help to personalize the issue being argued. An example should be clearly related to the argument, and it should be typical and representative, not an extreme, isolated case.
Statistics provide precise quantitative data that clarifies and supports claims.
Statistics should be understandable. Comparative statistics are helpful since they allow the audience to interpret the statistics in a meaningful way, determining if a statistical value is relatively high or low, great or small. The author should indicate the credentials of any expert used, giving the person s title or background. Authorities may be individuals, institutions, bodies, or documents seen as authoritative sources on the issue being argued. The American Medical Association, the US Constitution, the US Supreme Court all may be considered authoritative sources on relevant subjects.