Understand conditional probability

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Lesson Plan →Objectives, pacing and practice, built from this lesson's brief.
Guided Notes →One page your students fill in and keep.
Exit Ticket →Three items at the end of class. No student accounts.
Re-teach →After an exit ticket: who missed what, and what to do tomorrow.
Homework →Assign practice; it grades itself.

HSS.CP.A.3

**HSS.CP.A.3**: Understand the conditional probability of A given B as P(A and B)/P(B), and interpret independence of A and B as saying that the conditional probability of A given B is the same as the probability of A, and the conditional probability of B given A is the same as the probability of B.

HSS.CP.A.3: Understand the conditional probability of A given B as P(A and B)/P(B), and interpret independence of A and B as saying that the conditional probability of A given B is the same as the probability of A, and the conditional probability of B given A is the same as the probability of B.

What you'll learn

Define and compute the conditional probability P(A|B) using the formula P(A|B) = P(A and B) / P(B)
Explain in their own words why conditional probability represents "restricting the sample space" to only outcomes where B has occurred
Interpret independence of events A and B as the condition P(A|B) = P(A) - knowing B occurred doesn't change the probability of A
Determine whether two events are independent by checking if P(A|B) = P(A) or equivalently if P(A and B) = P(A) * P(B)
Apply conditional probability to real-world scenarios, including medical testing, quality control, and everyday decision making

Slides

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Formula and representations

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Independence and medical testing

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Practice

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Exercise

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