From
Sociology 371 -- Research Methods --
"The experimental design is not often used by sociologists. Rather, it is in psychology, where there is greater concern for internal validity, that we are more likely to find the experimental approach. That is not to say that sociologists are unconcerned with issues of internal validity, but sociology tends to emphasize issues of external validity and generalizability. This disciplinary emphasis seems to preclude the use of experimentation by most sociologists."