The Relationship between Internal and External Validity in the Experimental Research Method

The research problem is concerned with the relationship between internal and external validity. Generally it is said that there is an inverse relationship between internal and external validity. Criticizing the inverse relationship, the study supports that generally there is a direct relationship between internal and external validity. The main research method is literature review. The main materials are books and journal articles which are related with research method and research validity especially.
First of all the study brings out the problems which are incurred from the perspective of an inverse relationship. Then the author makes 2 arguments against the inverse relationship. That is, first there is no empirical data for the inverse relationship and the inverse relationship comes from the background of clinical research which is very different with educational research. Second, according to the logic of inverse relationship lab research is apt to have high internal validity and low external validity and field research is apt to have low internal validity and high external validity. However, Dipvoye et al. verified that there is no relationship between lab and field research, that is, internal and external validity.
Also the author makes 2 arguments for the direct relationship. That is, first there are very similar threats to internal and external validity. So internal and external validity can be increased or decreased by controlling the same threats at the same time. Second, there is high probability that the representativeness of sample could be sustained or increased through the control of critical factors. That is, the lab research could have high internal and external validity through even controls.