In psychology,<unk> has two distinct fields of application. The first involves test<unk>  a concept that has evolved with the field of psychometrics but which textbooks still commonly gloss as the degree to which a test measures what it was designed to measure. The second involves research design. Here the term refers to the degree to which a study supports the intended conclusion drawn from the results. In the Campbellian tradition, this latter sense divides into four aspects: support for the conclusion that the causal variable caused the effect variable in the specific study (internal<unk> , support that the same effect generalizes to the statistical population from which the sample was drawn (statistical conclusion<unk> , support for the intended interpretation of the variables (construct<unk> , and support for the generalization of the results beyond the statistical population (external<unk> .
Validity 
Specificity 
Unblinding
Causality
Cognitive bias
Providencia
Valence 
Relative volatility