Check your understanding
Quiz
You have learned what a causal effect really means through potential outcomes, how to read confounders and colliders off a causal diagram, how to design and size a fair A/B test, how to report an experiment's effect with honest uncertainty, and how to estimate effects when randomization is impossible. This quiz checks what stuck. The last two steps are live R you can run.
Question 1 of 6
What a causal effect is
In the potential-outcomes framing, the causal effect of a treatment on one unit is:
Correct: the effect compares two potential outcomes for the same unit, only one of which we ever observe.
A p-value measures evidence, not the effect itself.