Anecdotal evidence

What does Anecdotal evidence mean in American Law?

The definition of Anecdotal evidence in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

A term of abuse in assessing a social science argument, as in “These grand generalizations are not buttressed by any statistically significant collection of data, but on anecdotal evidence only.” The criticism is that not much in the way of generalization can safely be made of an incident or two. But it should also be recognized that much of what we know as individuals is, whether wisely or not, based on anecdotal evidence, e.g., the behavior of muggers when balked, or of lovers when jealously followed. The amount of statistically valid knowledge about ourselves and the world is in fact extremely small.