Placebo Test Example

• Research Question: “Does Wine cause Lifespan?”
• Placebo Test: “Are Drugs and Income related?”

open and closed paths

• 8/10 paths are closed because Lifespan is a collider

What if we control for Wine?

• But Wine seems necessary for the relationship between Income and Drugs (but Wine is a subset of Drugs)
• After controlling for Wine, there are no more Open paths (but the data would probably suggest a relationship)