Answer:
D) External; Internal
Explanation:
The External validity of a study refers to the relation the findings have with some general truth, or generalized worldview. For example, in a study about depression and time consumed playing videogames, the external validity could refer to the reasons why people who do not go outside a lot tend to be more depressed.
On the other hand, internal validity refers to the cause-and-effect relationship between the variables. This is difficult to establish, you need to verify that one variable preceeds the other, and that the change in one, changes the other.
From the above example, internal vailidy could be established if in a randomized experiment, people were told to play videogames a certain amount of hours a day, and after, they had their depression levels measured. If the more hours spent gaming meant more depression, then, internal validity between the two variables could be established in the experiment.
