options: 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.

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.

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”).

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.

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.
problem_activity: Problem 1
There are four red envelopes, four blue envelopes, and four $1 bills, which will be placed in four of the eight envelopes.
Below is a tree diagram we can use to answer the questions that follow. Write in the probabilities described.
Suppose one $1 bill is placed in a blue envelope, and the three remaining $1 bills are placed in three red envelopes.
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If you choose a blue envelope, what is the probability that you will get the $1?
If you choose a red envelope, what is the probability that you will get the $1?
Problem 2
Suppose the $1 bills are redistributed among the envelopes. Two $1 bills are placed in two blue envelopes, and two $1 bills are placed in two red envelops. Record the probabilities on the tree diagram.
[IMG]
If you choose a blue envelope, what is the probability that you will get the $1?
If you choose a red envelope, what is the probability that you will get the $1?


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