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The following table shows the distribution of Democratic and Republican U.S. Senators by gender.

MALE(M) FEMALE(F) TOTAL
DEMOCRATS(D) 39 4 43
REPUBLICANS(R) 52 5 57
TOTALS 91 9 100

Use this table to determine the following probabilities:

P M D size 12{P left (M \lline D right )} {}
39 / 43 size 12{"39"/"43"} {}
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P D M size 12{P left (D \lline M right )} {}
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P F R size 12{P left (F \lline R right )} {}

5 / 57

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P R F size 12{P left (R \lline F right )} {}
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Do the following conditional probability problems.

At De Anza College, 20% of the students take Finite Math, 30% take History, and 5% take both Finite Math and History. If a student is chosen at random, find the following conditional probabilities.

  1. He is taking Finite Math given that he is taking History.

  2. He is taking History assuming that he is taking Finite Math.

  1. 1 / 6 size 12{1/6} {}
  2. 1 / 4 size 12{1/"4"} {}
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At a college, 60% of the students pass Accounting, 70% pass English, and 30% pass both of these courses. If a student is selected at random, find the following conditional probabilities.

  1. He passes Accounting given that he passed English.

  2. He passes English assuming that he passed Accounting.

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If P F = . 4 size 12{P left (F right )= "." 4} {} and P E F = . 3 size 12{P left (E \lline F right )= "." 3} {} , find P E   and  F size 12{P left (E" and "F right )} {} .

0.12

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If P E = . 3 size 12{P left (E right )= "." 3} {} , and P F = . 3 size 12{P left (F right )= "." 3} {} , and E size 12{E} {} and F size 12{F} {} are mutually exclusive, find P E F size 12{P left (E \lline F right )} {} .

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If P E = . 6 size 12{P left (E right )= "." 6} {} and P E   and   F = . 24 size 12{P left (E" and "F right )= "." "24"} {} , find P F E size 12{P left (F \lline E right )} {} .

0.4

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If P E   and   F = . 04 size 12{P left (E" and "F right )= "." "04"} {} and P E F = . 1 size 12{P left (E \lline F right )= "." 1} {} , find P F size 12{P left (F right )} {} .

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Consider a family of three children. Find the following probabilities.

P two boys first born is a boy size 12{P left ("two boys" \lline "first born is a boy" right )} {}
2 / 4 size 12{2/4} {}
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P all girls at least one girl is born size 12{P left ("all girls " \lline " at least one girl is born" right )} {}
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P children of both sexes first born is a boy size 12{P left ("children of both sexes " \lline " first born is a boy" right )} {}
3 / 4 size 12{3/4} {}
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P all boys there are children of both sexes size 12{P left ("all boys " \lline " there are children of both sexes" right )} {}
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Independent events

The distribution of the number of fiction and non-fiction books checked out at a city's main library and at a smaller branch on a given day is as follows.

MAIN(M) BRANCH(B) TOTAL
FICTION(F) 300 100 400
NON-FICTION(N) 150 50 200
TOTALS 450 150 600

Use this table to determine the following probabilities:

P F size 12{P left (F right )} {}
2 / 3 size 12{2/3} {}
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P M F size 12{P left (M \lline F right )} {}
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P N B size 12{P left (N \lline B right )} {}
50 / 150 size 12{"50"/"150"} {}
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Is the fact that a person checks out a fiction book independent of the main library?

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For a two-child family, let the events E size 12{E} {} , F size 12{F} {} , and G size 12{G} {} be as follows.

E size 12{E} {} : The family has at least one boy F size 12{F} {} : The family has children of both sexes G size 12{G} {} : The family's first born is a boy

Find the following.

  1. P E size 12{P left (E right )} {}

  2. P F size 12{P left (F right )} {}

  3. P E F size 12{P left (E intersection F right )} {}

  4. Are E size 12{E} {} and F size 12{F} {} independent?

  1. 3 / 4 size 12{3/4} {}
  2. 2 / 4 size 12{2/4} {}
  3. 2 / 4 size 12{2/4} {}
  4. no
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Find the following.

  1. P F size 12{P left (F right )} {}

  2. P G size 12{P left (G right )} {}

  3. P F G size 12{P left (F intersection G right )} {}

  4. Are F size 12{F} {} and G size 12{G} {} independent?

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Do the following problems involving independence.

If P E = . 6 size 12{P left (E right )= "." 6} {} , P F = . 2 size 12{P left (F right )= "." 2} {} , and E size 12{E} {} and F size 12{F} {} are independent, find P E   and   F size 12{P left (E" and "F right )} {} .

0.12

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If P E = . 6 size 12{P left (E right )= "." 6} {} , P F = . 2 size 12{P left (F right )= "." 2} {} , and E size 12{E} {} and F size 12{F} {} are independent, find P E   or  F size 12{P left (E" or "F right )} {} .

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If P E = . 9 size 12{P left (E right )= "." 9} {} , P F E = . 36 size 12{P left (F \lline E right )= "." "36"} {} , and E size 12{E} {} and F size 12{F} {} are independent, find P F size 12{P left (F right )} {} .

0.36

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If P E = . 6 size 12{P left (E right )= "." 6} {} , P E   or   F = . 08 size 12{P left (E" or "F right )= "." "08"} {} , and E size 12{E} {} and F size 12{F} {} are independent, find P F size 12{P left (F right )} {} .

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In a survey of 100 people, 40 were casual drinkers, and 60 did not drink. Of the ones who drank, 6 had minor headaches. Of the non-drinkers, 9 had minor headaches. Are the events "drinkers" and "had headaches" independent?

Yes

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It is known that 80% of the people wear seat belts, and 5% of the people quit smoking last year. If 4% of the people who wear seat belts quit smoking, are the events, wearing a seat belt and quitting smoking, independent?

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John's probability of passing statistics is 40%, and Linda's probability of passing the same course is 70%. If the two events are independent, find the following probabilities.

  1. P both of them will pass statistics size 12{P left ("both of them will pass statistics" right )} {}

  2. P at least one of them will pass statistics size 12{P left ("at least one of them will pass statistics" right )} {}

  1. 28 / 100 size 12{"28"/"100"} {}
  2. 82 / 100 size 12{"82"/"100"} {}
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Source:  OpenStax, Applied finite mathematics. OpenStax CNX. Jul 16, 2011 Download for free at http://cnx.org/content/col10613/1.5
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