Statistical hypothesis test
A statistical hypothesis test is a method used in statistics to answer a question (the hypothesis), based on some data (information).
A statistical test works out a number which relates the information to the question. This is compared to other numbers. The critical value is the number which the test would give if the question was true. So if the statistical test gives a number close to the critical value, probably the answer to the question is true. But if the test gives a number very different from the critical value, probably the answer is false.