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Law of total probability in AP Statistics

A rule stating that the total probability of an event is the sum of probabilities of that event given each partition of the sample space, weighted by the probability of each partition.

Verified for the 2027 AP Statistics examLast updated August 2026

What is law of total probability?

A rule stating that the total probability of an event is the sum of probabilities of that event given each partition of the sample space, weighted by the probability of each partition.

In AP Statistics, this term belongs to 2.6 Conditional Probability. Use the notation and conditions attached to the procedure or model, then interpret the result in context.

Why law of total probability matters in AP® Statistics

law of total probability supports Unit 2: Probability, Random Variables, and Probability Distributions. The relevant CED learning objectives cover calculate conditional probabilities.

How law of total probability connects across the course

2.6 Conditional Probability

law of total probability is used in this topic. Connect the definition to the topic's calculations and interpretations in context.

Bayes' theorem (Unit 2)

Bayes' theorem appears with law of total probability in Topic 2.6. Use the two ideas together when a question moves from identifying the setup to interpreting the result.

Empirical Rule (Unit 2)

Empirical Rule connects to law of total probability through the course's focus on variation, calculation, and conclusions in context.

Is law of total probability on the AP® Statistics exam?

An AP question can ask you to calculate a probability or interpret a probability distribution in context. Name the concept precisely, show the relevant calculation when needed, and state the conclusion in the problem's context.

Key things to remember about law of total probability

  • A rule stating that the total probability of an event is the sum of probabilities of that event given each partition of the sample space, weighted by the probability of each partition.

  • law of total probability is mapped to 2.6 Conditional Probability in the current AP Statistics course.

  • On an AP question, use law of total probability as part of a complete calculation or interpretation, not as an isolated label.

Frequently asked questions about law of total probability

What is law of total probability in AP Statistics?

A rule stating that the total probability of an event is the sum of probabilities of that event given each partition of the sample space, weighted by the probability of each partition.

Which AP Stats unit covers law of total probability?

law of total probability appears in Unit 2: Probability, Random Variables, and Probability Distributions, especially 2.6 Conditional Probability.

How does law of total probability appear on the AP exam?

An AP question can ask you to calculate a probability or interpret a probability distribution in context. Name the concept precisely, show the relevant calculation when needed, and state the conclusion in the problem's context.

Is law of total probability only a vocabulary term?

No. Be ready to use it in a calculation, identify it in a setup, or interpret what it means in context.