• Entry
  • Reader's guide
  • Entries A-Z
  • Subject index

From a statistical perspective, causal inferences are strongest when drawn from a “randomized controlled experiment,” where the investigators assign subjects at random to a treatment condition or a control condition. Up to random error, randomization balances the two groups with respect to all factors—except for the particular causal factor under investigation. A significant difference between the two groups is therefore evidence of causation. For instance, one can assign heart attack patients to take aspirin (treatment) or not (control). Patients in the treatment group are less likely to experience adverse events. The difference shows that aspirin is protective.

Managing experiments is often complicated and expensive; sometimes, experiments are impractical or unethical. Investigators may turn instead to observational studies. In such a study, subjects assign themselves to

    • Loading...
    locked icon

    Sign in to access this content

    Get a 30 day FREE TRIAL

    • Watch videos from a variety of sources bringing classroom topics to life
    • Read modern, diverse business cases
    • Explore hundreds of books and reference titles