Final answer:
The relationship between control employed in a research study and external validity is a balance where high control can limit generalizability, while lower control may increase it but risk confounding variables.
Step-by-step explanation:
The relationship between the amount of control employed in a research study and the external validity is a trade-off. High control allows researchers to eliminate confounding variables, ensuring that the independent variable is the cause of any observed changes in the dependent variable. This tight control, however, often results in experiments being conducted in artificial settings, which can limit the external validity—the extent to which the results can be generalized beyond the experimental conditions. If a study has a high degree of control, particularly over the independent variables, it can result in an artificial environment that doesn't accurately reflect real-world conditions, thus lowering the external validity. On the other hand, experiments with less control that more closely mirror natural settings might increase external validity, despite the risk of introducing confounding variables.