Practice

Formulas

Union of non-disjoint events:

• P(A \(\cup\) B) = P(A) + P(B) - P(A \(\cap\) B)

Product rule for independent events:

• P(A \(\cap\) B) = P(A) × P(B)

Product rule for non-independent events:

• P(A \(\cap\) B) = P(A | B) x P(B)

Conditional probability:

• P(A|B) = P(A \(\cap\) B) / P(B)

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Contingency Table

Here’s the distribution of drinks (counts in thousands) and day types in the last few weeks for a coffee shop:

	Weekday	Weekend	Holiday	Total (Drink)
Coffee	10	5	15	30
Tea	5	10	10	25
Specialty Drink	10	20	15	45
Total (Day)	25	35	40	100