is the validity of generalized (causal) inferences in scientific
studies, usually based on experiments as experimental validity
.Mitchell, M. & Jolley, J. (2001). Research Design Explained
(4th Ed) Inferences about cause-effect relationships based on a
specific scientific study are said to possess external validity
if they may be generalized from the unique and idiosyncratic
settings, procedures and participants to other populations and
conditions.Brewer, M. (2000). Research Design and Issues of
Validity. In Reis, H. & Judd, C. (eds) Handbook of Research
Methods in Social and Personality Psychology.
Cambridge:Cambridge University Press.Shadish, W., Cook, T., &
Campbell, D. (2002). Experimental and Quasi-Experimental Designs
for Generalized Causal Inference Boston:Houghton Mifflin. Causal
inferences said to possess high degrees of external validity can
reasonably be expected to apply (a) to the target population of
the study (i.e. from which the sample was drawn) (also referred
to as population validity), and