Question 1

If P(A)  = .80, P(B)  = .65, and P(A ? B)  = .78, then P(B  ∣\mid  ∣  A)  = _____.

Accepted Answer

A)   .6700
B)   .8375
C)   .9750
D)   Not enough information is given to answer this question.

Question 2

A couple has three children. Assuming each child has an equal chance of being a boy or a girl, what is the probability that they have at least one girl?

Accepted Answer

A)   .125
B)   .5
C)   .875
D)   1

Question 3

If two events are independent, then _____.

Accepted Answer

A)   they must be mutually exclusive
B)   the sum of their probabilities must be equal to 1
C)   the probability of their intersection must be 0
D)   None of the answers is correct.

Question 4

If two events are mutually exclusive, then the probability of their intersection _____.

Accepted Answer

A)   will be equal to 0
B)   can have any value larger than 0
C)   must be larger than zero, but less than 1
D)   will be 1

Question 5

The probability of the intersection of two mutually exclusive events _____.

Accepted Answer

A)   can be any value between 0 and 1
B)   must always be equal to 1
C)   must always be equal to 0
D)   can be any positive value

Question 6

The probability of the occurrence of event A in an experiment is 1/3. If the experiment is performed two times and event A did not occur, then on the third trial event A _____.

Accepted Answer

A)   must occur
B)   may occur
C)   could not occur
D)   has a 2/3 probability of occurring

Question 7

The probability of the union of two events with nonzero probabilities _____.

Accepted Answer

A)   cannot be less than 1
B)   cannot be 1
C)   cannot be less than one and cannot be 1
D)   None of the answers is correct.

Question 8

If X and Y are mutually exclusive events with P(X)  = .295, P(Y)  = .32, then P(X ∪ Y)  = _____.

Accepted Answer

A)   .094
B)   .615
C)   1
D)   0

Question 9

Twenty percent of people at a company picnic got food poisoning. What percent of the people at the picnic did NOT get food poisoning?

Accepted Answer

A)   20%
B)   40%
C)   60%
D)   80%

Question 10

The probability of an event is _____.

Accepted Answer

A)   the sum of the probabilities of the sample points in the event
B)   the product of the probabilities of the sample points in the event
C)   the minimum of the probabilities of the sample points in the event
D)   the maximum of the probabilities of the sample points in the event

Question 11

Of the last 100 customers entering a computer shop, 25 have purchased a computer. If the relative frequency method for computing probability is used, the probability that the next customer will purchase a computer is _____.

Accepted Answer

A)   .25
B)   .50
C)   1
D)   .75

Question 12

The collection of all possible sample points in an experiment is _____.

Accepted Answer

A)   the sample space
B)   a sample point
C)   an experiment
D)   the population

Question 13

A magician holds a standard deck of cards and draws one card. The probability of drawing the ace of diamonds is 1/52. What method of assigning probabilities was used?

Accepted Answer

A)   objective method
B)   classical method
C)   subjective method
D)   experimental method

Question 14

On a December day, the probability of snow is .30. The probability of a "cold" day is .50. The probability of snow and a "cold" day is .15. Are snow and "cold" weather independent events?

Accepted Answer

A)   only if given that it snowed
B)   no
C)   yes
D)   only when they are also mutually exclusive

Question 15

Suppose we flip a fair coin five times and each time it lands heads up. The probability of landing heads up on the next flip is _____.

Accepted Answer

A)   1/2
B)   1
C)   0
D)   None of the answers is correct.

Question 16

Revised probabilities of events based on additional information are _____.

Accepted Answer

A)   joint probabilities
B)   posterior probabilities
C)   marginal probabilities
D)   complementary probabilities

Question 17

Posterior probabilities are _____.

Accepted Answer

A)   simple probabilities
B)   marginal probabilities
C)   joint probabilities
D)   conditional probabilities

Question 18

If P(A | B)  = 0.3,

Accepted Answer

A)   P(B | 
A)   = 0.7
B)   P(Ac | 
B)   = 0.7
C)   P(A | Bc)  = 0.7
D)   P(Ac | Bc)  = 0.7

Question 19

If A and B are independent events with P(A)  = .38 and P(B)  = .55, then P(A | B)  =

Accepted Answer

A)   .209
B)   0
C)   .550
D)   None of the answers is correct.

Question 20

Initial estimates of the probabilities of events are known as _____.

Accepted Answer

A)   sets
B)   posterior probabilities
C)   conditional probabilities
D)   prior probabilities

Exam 4: Introduction to Probability

A magician holds a standard deck of cards and draws one card. The probability of drawing the ace of diamonds is 1/52. What method of assigning probabilities was used?

Correct AnswerverifiedShow Answer

Of the last 100 customers entering a computer shop, 25 have purchased a computer. If the relative frequency method for computing probability is used, the probability that the next customer will purchase a computer is _____.

Correct AnswerverifiedShow Answer

If X and Y are mutually exclusive events with P(X) = .295, P(Y) = .32, then P(X ∪ Y) = _____.

Correct AnswerverifiedShow Answer

The probability of the intersection of two mutually exclusive events _____.

Correct AnswerverifiedShow Answer

The probability of the union of two events with nonzero probabilities _____.

Correct AnswerverifiedShow Answer

If P(A | B) = 0.3,

Correct AnswerverifiedShow Answer

Revised probabilities of events based on additional information are _____.

Correct AnswerverifiedShow Answer

The probability of the occurrence of event A in an experiment is 1/3. If the experiment is performed two times and event A did not occur, then on the third trial event A _____.

Correct AnswerverifiedShow Answer

If P(A) = .80, P(B) = .65, and P(A ? B) = .78, then P(B ∣\mid ∣ A) = _____.

Correct AnswerverifiedShow Answer

A couple has three children. Assuming each child has an equal chance of being a boy or a girl, what is the probability that they have at least one girl?

Correct AnswerverifiedShow Answer

Twenty percent of people at a company picnic got food poisoning. What percent of the people at the picnic did NOT get food poisoning?

Correct AnswerverifiedShow Answer

On a December day, the probability of snow is .30. The probability of a "cold" day is .50. The probability of snow and a "cold" day is .15. Are snow and "cold" weather independent events?

Correct AnswerverifiedShow Answer

If two events are mutually exclusive, then the probability of their intersection _____.

Correct AnswerverifiedShow Answer

The collection of all possible sample points in an experiment is _____.

Correct AnswerverifiedShow Answer

The probability of an event is _____.

Correct AnswerverifiedShow Answer

Posterior probabilities are _____.

Correct AnswerverifiedShow Answer

Suppose we flip a fair coin five times and each time it lands heads up. The probability of landing heads up on the next flip is _____.

Correct AnswerverifiedShow Answer

Initial estimates of the probabilities of events are known as _____.

Correct AnswerverifiedShow Answer

If A and B are independent events with P(A) = .38 and P(B) = .55, then P(A | B) =

Correct AnswerverifiedShow Answer

If two events are independent, then _____.

Correct AnswerverifiedShow Answer

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If P(A) = .80, P(B) = .65, and P(A ? B) = .78, then P(B $\mid$ A) = _____.

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