4. DO NOT USE ANECDOTAL EVIDENCE TO PROVE A POINT
Anecdotal evidence proves nothing. Well, perhaps we're being too hasty. If we assume that the anecdotal evidence we are hearing is true, we could use it to disprove a universal claim. For example, if someone claims that all midgets are blind, you could disprove the claim by reporting that you have a cousin who is a sighted midget. If we assume that you are speaking the truth, then it cannot be true that all midgets are blind. What we could not do is extrapolate from the happy case of your cousin to a statement about the sightedness of midgets in general.
In most contexts, anecdotal evidence is worse than useless, because it is misleading. If there are fifty people in a room, and ten of them have little stories to share about the warmth and compassion of Texans, should we take their stories as evidence for the proposition that most Texans are warm and compassionate? Of course we shouldn't; we haven't heard about even a tiny fraction of the Texans in the world. In this case, we've only heard about a portion of the behavior of Texans met by ten people. Those Texans could have been vicious at other times (see, e.g., the Alamo). In any event, the time spent listening to the ten people's stories is wasted time, if the purpose of the discussion is to establish some general factual proposition about Texans.
