External Validity

External validity refers to the generalizability or representativeness of experimental effects or program treatments. There are several questions of representativeness that could be posed concerning the results of experimental or evaluation studies: (a) To what other groups do the study results apply, or to what population can they be generalized? These are questions of sample generalizabilty. (b) To what other experimental or social settings and programs do the results apply? Such questions are addressing issues of ecological representativeness. (c) Do the treatment or independent variables used in the study represent factors that are unique to the study (or program) or represent a stable class of variables that are universal? For example, if the construct of “respect for authority” was assessed with an attitudinal scale, would ...