What is the relationship between moderators and external validity? group of answer choices a) moderators suggest that associations may not generalize to all subgroups of people. b) moderators suggest that an association between two variables will extend to another variable. c) moderators suggest that associations may be spurious. d) moderators are necessary for external validity to be established.

Martha participates in a research study in order to receive extra credit for her psychology class. when she arrives in the research office she is given a can of what looks and tastes like beer, but which actually contains no alcohol. in the adjoining room martha's classmate karen is also participating in the study. karen receives a can of alcoholic beer. if the experiment was designed to test the effects of alcohol on concentration, then who is exposed to the independent variable?