Which of the following is NOT listed as a component of a theory?

• A. Hypothesis
• B. Variable
• C. Concept
• D. Extraneous variable

Answer: (D)

A theory is built from the core ideas it uses to explain phenomena: concepts are the abstract building blocks, variables are how those ideas are measured or manipulated, and hypotheses are testable statements about how those variables relate. Extraneous variables, on the other hand, are factors outside the theory’s structure that can affect outcomes in a study. They’re research-design concerns—things to control or account for in order to test the theory cleanly—not components that compose the theory itself. So extraneous variables aren’t listed as a part of the theory, while concepts, variables, and hypotheses are.