Mathematics II Conditional Probability and the Rules of Probability

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Resources

Understand independence and conditional probability and use them to interpret data. [Link to data from simulations
or experiments.]
1. Describe events as subsets of a sample space (the set of outcomes) using characteristics (or categories) of the outcomes,
or as unions, intersections, or complements of other events (“or,” “and,” “not”).
2. Understand that two events A and B are independent if the probability of A and B occurring together is the product of their
probabilities, and use this characterization to determine if they are independent.
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.
4. Construct and interpret two-way frequency tables of data when two categories are associated with each object being
classified. Use the two-way table as a sample space to decide if events are independent and to approximate conditional
probabilities. For example, collect data from a random sample of students in your school on their favorite subject among
math, science, and English. Estimate the probability that a randomly selected student from your school will favor science
given that the student is in tenth grade. Do the same for other subjects and compare the results.
5. Recognize and explain the concepts of conditional probability and independence in everyday language and everyday
situations.
Use the rules of probability to compute probabilities of compound events in a uniform probability model.
6. Find the conditional probability of A given B as the fraction of B’s outcomes that also belong to A, and interpret the answer
in terms of the model.

7. Apply the Addition Rule, P(A or B) = P(A) + P(B) – P(A and B), and interpret the answer in terms of the model.
8. (+) Apply the general Multiplication Rule in a uniform probability model, P(A and B) = P(A)P(B|A) = P(B)P(A|B), and
interpret the answer in terms of the model.

9. (+) Use permutations and combinations to compute probabilities of compound events and solve problems.