Joint probability distributions

Joint probability distributions

Consider two ‘experiments’ at the same time

• Joint distributions describe how the outcomes of two experiments behave together

• We summarize joint behavior in a two-way contingency table

• Example: Graduate School Admissions

Joint probabilities

Consider two outcomes together, simultaneously:

• P(Male AND Accepted)

• P(Female AND Rejected)

Marginal probabilities

Consider only one of the outcomes, other is not known

• P(Male) =

• P(Accepted)

Conditional probabilities

In general: P(A | B) = P(A and B) / P(B)

Relative risk

(Risk ratio)

Relative risk (Risk ratio)