Ch. 6 Quiz and Study Guide

Question 1

Which of the following is a valid probability value for a discrete random variable?
a.) .2
b.) 1.01
c.) −.7
d.) All of the choices are correct.

Answer 1

a.) .2

(is not c because p(x) has to be greater than or equal to 0, and isn’t b because the sum of all the probabilities must = to 1)

Question 2

The variable Employment Status, which can take either the value 1 for Employed or 0 for Unemployed, is an example of a ________ random variable.
a.) Poisson
b.) discrete
c.) hypergeometric
d.) continuous

Answer 2

b.) discrete

Question 3

If x is a binomial random variable, then the standard deviation of x is given by:
a.) n x p
b.) (npq)^2
c.) √npq
d.) n x p x q

Answer 3

c.) √npq

(the square root of n times p times q)

Question 4

A discrete variable that can often be used to describe the number of occurrences of an event over a
specified interval of time or space is a ________ random variable.
a.) Poisson
b.) discrete
c.) hypergeometric
d.) continuous

Answer 4

a.) Poisson

Question 5

A random variable that is defined to be the total number of successes in n trials is a ________ random variable.
a.) binomial
b.) Poisson
c.) hypergeometric
d.) continuous

Answer 5

a.) binomial

Question 6

When p = .5, the binomial distribution will ________ be symmetric.
a.) always
b.) sometimes
c.) never

Answer 6

a.) always

(write on cheat sheet prob)

Question 7

A fair die is rolled 10 times. What is the average number of even number outcomes?
a.) 3
b.) 4
c.) 5
d.) 6
e.) 7

Answer 7

c.) 5

Binomial Mean = n x p = 10 x (.5) = 5

(maybe write on cheat sheet)

Question 8

A fair die is rolled 36 times. What is the standard deviation of the even number (2, 4, or 6) outcomes?
a.) 18
b.) 9
c.) 4.243
d.) 3
e.) 1.732

Answer 8

d.) 3

Question 9

The probability that a given computer chip will fail is .02. Find the probability that of 5 delivered
chips, exactly 2 chips will fail.
a.) .9962
b.) .0999
c.) .0038
d.) .0000

Answer 9

c.) .0038

(use the binomial distribution formula)

Question 10

The J.O. Supplies Company buys calculators from a non-U.S. supplier. The probability of a defective
calculator is 10 percent. If 100 calculators are selected at random, what is the expected number of
defectives?
a.) 9
b.) 90
c.) 10
d.) 95

Answer 10

c.) 10

(Do x times p(x), which is 100 x .10 = 10)

Question 11

Which of the following is not a discrete random variable?
a.) the number of times a light changes red in a 10-minute cycle.
b.) the number of minutes required to run 1 mile.
c.) the number of defects in a sample selected from a population of 100 products.
d.) the number of criminals found in a five-mile radius of a neighborhood

Answer 11

b.) the number of minutes required to run 1 mile.

Question 12

A random variable…
a.) is the result of a measurement.
b.) can only be discrete.
c.) assigns one and only one numeric value to each experimental outcome.
d.) is a binomial, Poisson, or hypergeometric variable.

Answer 12

c.) assigns one and only one numeric value to each experimental outcome.

Question 13

A discrete probability distribution is expressed as a table, graph, or ________ that gives the probability associated with each possible value that the random variable can assume.
a.) binomial
b.) formula
c.) Poisson
d.) hypergeometric

Answer 13

b.) formula

Question 14

The requirement that the probability of success remains constant from trial to trial is a property of the _________ distribution.
a.) binomial
b.) uniform
c.) normal
d.) Poisson

Answer 14

a.) binomial