Types of Inductive Evidence

Type	Definition	Evaluation
Counterexample	An example contradicting the thesis	Must be genuine Must be reliable
Sample	Example drawn from a larger group	Must be representative
Experimentation	Application of scientific method	Requires extensive and repeated observations Requires careful control of variables in order to justify conclusions
Example	Illustration to prove a point	Must be relevant Must be specific to the situation
Real event	An actual event illustrating the thesis	May be more complex than the point to be proven
Hypothetical situation	Constructed example	Must be reasonable Are suggestive, but not evidence May not be convincing May help clarify a position
Analogy	Extended comparison	Inappropriate similarities may be drawn Contexts may be too dissimilar
Authoritative Testimony	Evidence provided by an expert in a particular field	Must be authority on issue in question Must not be biased Must be recognizable authority (avoid nameless authorities) Must be up-to-date Must be an authority recognized as valid/valuable by audience
Personal Testimony	The experience of some individual (the writer or some other)	Must be relevant Must be authoritative
Statistics	Numerical and graphical data	Must verify the source and reliability of statistics used Must understand the differences between types of statistics Median--middle value in a distribution Mean--sum of items divided by number of items Mode--most repeated value in a distribution Range--the difference between the largest and smallest value Must not assume relationships like cause/effect Must be an adequate sample -size and representation Must be recent enough to be relevant Must be quantifiable Must include all relevant factors

This chart defines various types of inductive evidence (evidence based on observation) and indicates qualifications which may apply.
This information is based on a summary of Sylvia Barnet and Hugo Bedau, Critical Thinking, Reading, and Writing: A Critical Guide to Argument, pages 63-72.