A significance test can be described as either directional or nondirectional. Any test capable of the specification of a direction is a one-tailed test when the specification is used. Notably, these tests are often associated with the use of a hypothesis to test some description of an expected relationship. A nondirectional test, which is usually part of a research question, employs what is described as a two-tailed test. This entry introduces directional and nondirectional testing, discusses the difference between a hypothesis and research question, and explores some of the circumstances under which one might use a one-tailed test, paying specific attention to the context of communication research.