Internal and External Validity

Question 1

What is internal validity?

Answer 1

Cause and effect (Did the treatments (IV) cause the change in the outcome (DV)?) it is to address the true cause of the outcome.

Question 2

What is external validity?

Answer 2

To what populations, settings, or treatments can the outcome be generalized?

Question 3

Is there a trade-off between internal and external validity?

Answer 3

Yes, the more internally valid less generalization to be made

Question 4

How to control threats to internal validity?

Answer 4

Randomization, Placebos, Blind Setups, Double-blind setups, Reactive effects of testing: estimate pretest, Instrumentation, experimental mortality

Question 5

How to control threats to external validity?

Answer 5

Selecting from a larger population, ecological validity: does the setting capture the essence of the real world?

Question 6

Internal Validity example

Answer 6

strong justification that causally links your IV to your DV

Question 7

External Validity example

Answer 7

Target population