Ch. 7 Quiz and Study Guide

Question 1

A study shows that employees who begin their workday at 9:00 a.m. vary their times of arrival
uniformly from 8:40 a.m. to 9:30 a.m. The probability that a randomly chosen employee reports to
work between 9:00 and 9:10 is
a.) 40 percent.
b.) 20 percent.
c.) 10 percent.
d.) 30 percent.
e.) 16.7 percent.

Answer 1

b.) 20 percent.

(P(9:00<x<9:10) = 10 min / 50 min = 1/5 = 20%)

Question 2

If the random variable x is normally distributed, _______ percent of all possible observed values of x will be within three standard deviations of the mean.
a.) 68.26
b.) 95.44
c.) 99.73
d.) 100
e.) none of these answers are correct

Answer 2

c.) 99.73

Question 3

The z-value tells us the number of ______ that a value of x is from the mean.
a.) variances
b.) standard deviations
c.) medians
d.) standard means

Answer 3

b.) standard deviations

Question 4

A continuous probability distribution having a rectangular shape, where the probability is evenly
distributed over an interval of numbers is a(n) ________ distribution.
a.) exponential
b.) binomial
c.) normal
d.) uniform

Answer 4

d.) uniform

Question 5

The specific shape of each normal distribution is determined by its ________ and ________.
a.) mean, standard deviation
b.) median, standard deviation
c.) mean, variance
d.) median, variance

Answer 5

a.) mean, standard deviation

Question 6

The number of standard deviations that a value, x, is from the mean is a(n) ________.
a.) variance
b.) exponential value
c.) z score
d.) area

Answer 6

c.) z score

Question 7

A normal distribution with mean equal to zero and a standard deviation equal to one is called the
________ normal distribution.
a.) continuous
b.) uniform
c.) exponential
d.) standard

Answer 7

d.) standard

Question 8

The thickness of a randomly selected metal piece is a ________ random variable.
a.) Poisson
b.) continuous
c.) discrete
d.) binomial

Answer 8

b.) continuous

(can measure)

Question 9

________ values of the standard deviation result in a normal curve that is wider and flatter.
a.) Smaller
b.) Equal
c.) Larger
d.) Uniform

Answer 9

c.) Larger

Question 10

It is appropriate to use the uniform distribution to describe a continuous random variable x when:
a.) the area under the probability curve = 1
b.) the probability curve f(x)>0
c.) the shape of the histogram of all possible values of x is non-symmetrical
d.) relative frequencies of all possible values of x are about the same

Answer 10

d.) relative frequencies of all possible values of x are about the same

Question 11

The area under the normal curve between z=0 and z=1 is _________ the area under the normal curve between z=1 and z=2.
a.) less than
b.) greater than
c.) equal to
d.) less than, greater than, or equal to, depending on the value of the mean.
e.) less than, greater than, or equal to, depending on the value of the standard deviation

Answer 11

b.) greater than

Question 12

Values of the standard normal random variable are measured:
a.) with reference to specific units.
b.) in the units in which the mean is measured.
c.) in the number of standard deviations from the mean.
d.) in squared units in which the mean is measured.
e.) None of these answers are correct.

Answer 12

c.) in the number of standard deviations from the mean.

Question 13

Which of the following is a continuous distribution?
a.) Poisson
b.) hyper-geometric
c.) uniform
d.) binomial

Answer 13

c.) uniform