ACT Preparation / Unit 15 ACT 1426 short lesson, about 20 seconds
Conditional Probability and Two-Way Tables
Captions available
The idea
A conditional probability, P(A given B), restricts attention to the cases where B is true: P(A given B) = P(A and B)/P(B). In a two-way table, B's row or column gives the total.
In practice
Of 50 seniors, 30 drive: P(drives given senior) = 30/50 = 3/5.
Where people slip
P(A given B) and P(B given A) usually differ, because their denominators are different groups.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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