Conditional Probability and the Rules of Probability

Describe categories of events as subsets of a sample space using unions, intersections, or complements of other events (or, and, not).

Understand that if two events A and B are independent, the probability of A and B occurring together is the product of their probabilities, and that if the probability of two events A and B occurring together is the product of their probabilities, the two events are independent.

Understand the conditional probability of A given B as P (A and B)/P(B)Interpret independence of A and B in terms of conditional probability; that is, 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.

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, use collected 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.

Recognize and explain the concepts of conditional probability and independence in everyday language and everyday situations. For example, compare the chance of having lung cancer if you are a smoker with the chance of being a smoker if you have lung cancer.

Find the conditional probability of A given B as the fraction of Bs outcomes that also belong to A, and interpret the answer in context.

Apply the Addition Rule, P(A or B) = P(A) + P(B) P(A and B), and interpret the answers in context.

Apply the general Multiplication Rule in a uniform probability model, P(A and B) = [P(A)]x[P(B|A)] =[P(B)]x[P(A|B)], and interpret the answer in terms of the model.

Use permutations and combinations to compute probabilities of compound events and solve problems.