Final answer:
A study has internal validity if it can confirm a cause-effect relationship between the independent and dependent variables. Internal validity is a key concept in experimental research design to ensure causal inferences are justified.
Step-by-step explanation:
In terms of experimental research designs, a study has internal validity if a cause-effect relationship actually exists between the independent and dependent variables. The correct answer is A) Internal. Internal validity refers to the degree to which a study can establish a causal relationship between the independent and dependent variables, ensuring that the observed effects are indeed due to the manipulation of the independent variable and not due to extraneous factors.
To establish internal validity, researchers employ strategies such as random assignment to groups, controlling for extraneous variables, and using a controlled experiment. This allows for the conclusion that differences in the dependent variable are directly caused by the independent variable. Another aspect of experimental design is ensuring that the measurements taken are reliable and valid, which means that they are consistent and accurately measure the topic of the study, respectively.