Sometimes described as “statistical conclusion validity,” the validity of research conclusions refers to the degree to which the conclusions made about the null hypothesis are reasonable or correct. Because the null hypothesis typically states that a relationship between two variables does not exist, the validity of a research conclusion also refers to whether a relationship exists between two variables. Although the validity of research conclusions is distinct from construct validity and external validity, it is important to distinguish conclusion validity clearly from internal validity. Internal validity involves whether a relationship between two variables is a plausibly causal one. The validity of a research conclusion is concerned only with the presence or absence of a relationship between two variables. Thus, conclusion validity answers the most basic ...