Let's do a quick review of three common types of validity: Internal, External, and Construct.

• Internal Validity: When you think about internal validity, think INSIDE the experiment. Is your experiment so well designed that when the results are in, you feel confident that you can make truthful and definite statements about what happened in your study? If your study is relatively free of confounds, you will have high confidence in its results. That's internal validity.
  
  
• External Validity: Can your results be generalized to people outside of your study?
  
  
• Construct Validity: You are manipulating and measuring many concepts in your study – are you really tapping into these concepts?