Question 1

The probability that an Oxnard University student is carrying a backpack is .70. If 10 students are observed at random, what is the probability that fewer than 7 will be carrying backpacks?

Accepted Answer

A) .3504 
B) .2001 
C) .6177 
D) .2668

Question 2

Which model best describes the number of births in a hospital until the first twins are delivered?

Accepted Answer

A) Binomial 
B) Poisson 
C) Hypergeometric 
D) Geometric

Question 3

The Poisson distribution is appropriate to describe the number of babies born in a small hospital on a given day.

Accepted Answer

A) True 
 B)False

Question 4

The expected value (mean) of a binomial variable is 15. The number of trials is 20. The probability of "success" is:

Accepted Answer

A) .25 
B) .50 
C) .75 
D) .30

Question 5

On a Sunday in April, dog bite victims arrive at Carver Memorial Hospital at a historical rate of 0.6 victim per day. On a given Sunday in April, what is the probability that exactly two dog bite victims will arrive?

Accepted Answer

A) .0875 
B) .0902 
C) .0988 
D) .0919

Question 6

If X is a discrete uniform random variable ranging from 12 to 24, its mean is:

Accepted Answer

A) 18.5 
B) 16.0 
C) 18.0 
D) 19.5.

Question 7

Which model best describes the number of nonworking web URLs ("This page cannot be displayed") you encounter in a randomly chosen minute while surfing websites for Florida vacation rental condos?

Accepted Answer

A) Binomial 
B) Poisson 
C) Hypergeometric 
D) Geometric

Question 8

Ten percent of the corporate managers at Axolotl Industries majored in humanities. What is the expected number of managers to be interviewed until finding the first one with a humanities major?

Accepted Answer

A) 15 
B) 20 
C) 10 
D) 17

Question 9

The probability that a customer will use a stolen credit card to make a purchase at a certain Target store is 0.003. If 400 purchases are made in a given day, what is the approximate Poisson probability that 4 or fewer will be with stolen cards?

Accepted Answer

A) .0053 
B) .0076 
C) .9923 
D) .0555

Question 10

Which model best describes the number of incorrect fare quotations by a well-trained airline ticket agent between 2 p.m. and 3 p.m. on a particular Thursday?

Accepted Answer

A) Binomial 
B) Poisson 
C) Hypergeometric 
D) Geometric

Question 11

Of the following, the one that most resembles a Poisson random variable is the number of:

Accepted Answer

A) heads in 200 flips of a fair coin. 
B) annual power failures at your residence. 
C) face cards in a bridge hand of 13 cards. 
D) defective CDs in a spool containing 15 CDs.

Question 12

A carnival has a game of chance: a fair coin is tossed. If it lands heads you win $1.00, and if it lands tails you lose $0.50. How much should a ticket to play this game cost if the carnival wants to break even?

Accepted Answer

A) $0.25 
B) $0.50 
C) $0.75 
D) $1.00

Question 13

Which statement is incorrect?

Accepted Answer

A) The Poisson distribution is always skewed right. 
B) The binomial distribution may be skewed left or right. 
C) The discrete uniform distribution is always symmetric. 
D) The hypergeometric distribution is symmetric.

Question 14

The Poisson distribution has only one parameter.

Accepted Answer

A) True 
 B)False

Question 15

The coefficient of variation for a Poisson distribution with λ = 5 is:

Accepted Answer

A) 35.2 percent. 
B) 58.9 percent. 
C) 44.7 percent. 
D) 31.1 percent.

Question 16

The discrete random variable X is the number of students that show up for Professor Smith's office hours on Monday afternoons. The table below shows the probability distribution for X. What is the probability that fewer than 2 students come to office hours on any given Monday? $$\begin{array} { l c c c c r } 
X & 0 & 1 & 2 & 3 & \text { Total } \
P ( X ) & 40 & 30 & 20 & 10 & 1.00
\end{array}$$

Accepted Answer

A) .10 
B) .40 
C) .70 
D) .90

Question 17

Which is not a discrete random variable?

Accepted Answer

A) The number of births in a hospital on a given day 
B) The number of fives obtained in four rolls of a die 
C) The hourly earnings of a call center employee in Boston 
D) The number of applicants applying for a civil service job

Question 18

If X is a discrete uniform random variable ranging from one to eight, find P(X < 6).

Accepted Answer

A) .6250 
B) .5000 
C) .7500 
D) .3750

Question 19

Which probability model would you use to describe the number of customers served at a certain California Pizza Kitchen until the first customer orders split pea soup?

Accepted Answer

A) Binomial 
B) Geometric 
C) Uniform 
D) Poisson

Question 20

The Poisson distribution can be skewed either left or right, depending on λ.

Accepted Answer

A) True 
 B)False

Exam 6: Discrete Probability Distributions

The probability that an Oxnard University student is carrying a backpack is .70. If 10 students are observed at random, what is the probability that fewer than 7 will be carrying backpacks?

Which model best describes the number of births in a hospital until the first twins are delivered?

The Poisson distribution is appropriate to describe the number of babies born in a small hospital on a given day.

The expected value (mean) of a binomial variable is 15. The number of trials is 20. The probability of "success" is:

On a Sunday in April, dog bite victims arrive at Carver Memorial Hospital at a historical rate of 0.6 victim per day. On a given Sunday in April, what is the probability that exactly two dog bite victims will arrive?

If X is a discrete uniform random variable ranging from 12 to 24, its mean is:

Which model best describes the number of nonworking web URLs ("This page cannot be displayed") you encounter in a randomly chosen minute while surfing websites for Florida vacation rental condos?

Ten percent of the corporate managers at Axolotl Industries majored in humanities. What is the expected number of managers to be interviewed until finding the first one with a humanities major?

The probability that a customer will use a stolen credit card to make a purchase at a certain Target store is 0.003. If 400 purchases are made in a given day, what is the approximate Poisson probability that 4 or fewer will be with stolen cards?

Which model best describes the number of incorrect fare quotations by a well-trained airline ticket agent between 2 p.m. and 3 p.m. on a particular Thursday?

Of the following, the one that most resembles a Poisson random variable is the number of:

A carnival has a game of chance: a fair coin is tossed. If it lands heads you win $1.00, and if it lands tails you lose $0.50. How much should a ticket to play this game cost if the carnival wants to break even?

Which statement is incorrect?

The Poisson distribution has only one parameter.

The coefficient of variation for a Poisson distribution with λ = 5 is:

Which is not a discrete random variable?

If X is a discrete uniform random variable ranging from one to eight, find P(X < 6) .

Which probability model would you use to describe the number of customers served at a certain California Pizza Kitchen until the first customer orders split pea soup?

The Poisson distribution can be skewed either left or right, depending on λ.