We matched patients on age and sex. Is that enough?
A researcher cannot run a randomized trial, so instead compares patients who took a new drug with untreated patients, carefully matching each treated patient to an untreated one of the same age and sex. The treated group does better, and the researcher claims the drug works.
Why does matching on age and sex fall short of what randomization provides?
Your answer
This one is open-ended. Work it through, then check your reasoning against the full solution.