6'2 continued

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6.2 continued

• AP Stats

2
Probability

• All probabilities are numbers between 0 and 1.
• The sum of all possible outcomes have a
  probability value of 1.
• The probability that an event does not occur is 1
  minus the probability that it will occur. This is
  called the complement. Ac.
• If two events have no outcomes in common, the
  probability that one or the other occurs is the
  sum of their individual outcomes.

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Example

• If the probability of me coloring my hair purple
  is .3021 and the probability of Laura wearing
  sneakers to school is .4302, then the probability
  of event A or event B is .7323.

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Venn Diagrams

• The total sample space is denoted with a square.
  Each event is a circle. If the events could
  happen together, then overlap the circles.
• If they cannot overlap, then denote the problem
  with the symbol

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The Complement

• The sum of event A and its complement is equal to
  1.
• So what would a Venn Diagram of this look like?

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Turn to page 348
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Independence and Multiplication Rule

• If two events A and B are independent, then
• P(A and B) P(A)P(B)
• Ex If the probability of choosing Barack Obama
  for president is .65 and the probability of
  falling while walking into the polling booth is
  .02, then the Probability of voting for Obama and
  falling is
• (.65)(.02) .013

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Disjoint Events

• Disjoint describes the situation where the fact
  that event A happens means that even B cannot
  happen.
• Ex Event A snowing outside
• Event B 97 degrees Fahrenheit outside.
• To prove two events are disjoint,
• P(A or B) P(A) P(B)

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Homework

• 20, 22, 23, 26, 28, 30
• Do the problem, then check the answer in the
  back. If you get it right, congratulations! If
  you get it wrong, try to figure out how they got
  their answer.