Table 1.

Four Main Dimensions of Validity

Validity Type	Definition
Internal validity	The integrity of research procedures to produce accurate statements about the effects of a treatment or other manipulation, often stated as whether the empirical relationship between treatment and outcome can be considered causal
Construct validity	The accuracy of measures used to assess the domains or outcomes that are expected to change with treatment, and the accuracy of procedures represent the treatment construct
Statistical conclusion validity	The appropriateness of the statistical procedures used for determining the association between the treatment and outcomes.
External validity	Generalizability of the experiment to the population of interest and to other settings, treatments and outcomes

Source: Shadish et al. (2001).