- e.g., UC Berkeley's alleged sex bias in graduate admission (Science - 1975). Overall data showed a higher rate of admission among male applicants, but, broken down by departments, data showed a slight bias in favor of admitting female applicants.
- e.g., "reverse regression" (1970-80): Should one, in salary discrimination cases, compare salaries of equally qualified men and women, or, instead, compare qualifications of equally paid men and women. (Opposite conclusions.)
- Practical Dilemma: Why break down by department?
How about by some other variable Z?
Find Z such that P(y|do(x)) = Ŕz P(y|x,z)P(z)
- Solution: The back-door algorithm (Chapter 3).