How do I test critical thinking?

The most effective way to measure critical thinking is to use a critical thinking skills test to evaluate a person's core skills in analysis, inference, evaluation, deductive reasoning and inductive reasoning AND to use a critical thinking dispositional or attribute measure to assess the level of the person's consistent internal motivation or willingness to use his or her critical thinking skills when it counts in problem solving and decision making. That way you'll have an assessment of test takers' ability and willingness to use critical thinking.