Question 1 of 20
0.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
The personnel department of a large corporation wants to
estimate the family dental expenses of its employees to determine the
feasibility of providing a dental insurance plan. A random sample of 12
employees reveals the following family dental expenses (in dollars): 115, 370,
250, 593, 540, 225, 177, 425, 318, 182, 275, and 228.
Construct a 99% confidence interval estimate for the
standard deviation of family dental expenses for all employees of this
corporation.
Place your LOWER limit, in dollars rounded to 1 decimal
place, in the first blank. Do not use a dollar sign, a comma, or any other
stray mark. For example, 98.4 would be a legitimate entry. Correct175.5
Place your UPPER limit, in dollars rounded to 1 decimal
place, in the second blank. Do not use a dollar sign, a comma, or any other
stray mark. For example, 567.8 would be a legitimate entry. Correct440.8
Answer Key:
Question 2 of 20
0.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
Senior management of a consulting services firm is concerned
about a growing decline in the firm’s weekly number of billable hours. The firm
expects each professional employee to spend at least 40 hours per week on work.
In an effort to understand this problem better, management would like to estimate
the standard deviation of the number of hours their employees spend on
work-related activities in a typical week. Rather than reviewing the records of
all the firm’s full-time employees, the management randomly selected a sample
of size 51 from the available frame. The sample mean and sample standard
deviations were 48.5 and 7.5 hours, respectively.
Construct a 90% confidence interval for the standard
deviation of the number of hours this firm’s employees spend on work-related
activities in a typical week.
Place your LOWER limit, in hours, rounded to 1 decimal
place, in the first blank. For example, 6.7 would be a legitimate entry. Correct46.8
Place your UPPER limit, in hours, rounded to 1 decimal
place, in the second blank. For example, 12.3 would be a legitimate entry. Correct50.2
Answer Key:
Question 3 of 20
0.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
The manufacturer of a new compact car claims the miles per
gallon (mpg) for the gasoline consumption is mound-shaped and symmetric with a
mean of 25.9 mpg and a standard deviation of 9.5 mpg. If 30 such cars are
tested, what is the probability the average mpg achieved by these 30 cars will
be greater than 28?
Answer:
Correct.1037 Round your answer to
4 decimal places as necessary. For
example, 0.1357 would be a legitimate entry.
Answer Key:
Feedback: This is a sampling distribution problem with ? =
25.9. ? = 9.5, and sample size n = 30.
f[z=frac{28-25.9}{9.5/sqrt{30}} = 1.210755f]
P(z > 1.210755) = 1 – NORMSDIST(1.210755) = 0.1130
Or you can compute the probability without having to compute
z first:
P(x-bar > 28) = 1 – NORMDIST(28, 25.9, 9.5/SQRT(30),
TRUE) = 0.1130
Question 4 of 20
1.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
You are told that a random sample of 150 people from Iowa
has been given cholesterol tests, and 60 of these people had levels over the
“safe” count of 200. Construct a 95% confidence interval for the population
proportion of people in Iowa with cholesterol levels over 200. Place your LOWER
limit, rounded to 3 decimal places, in the first blank Correct.322 .
For example, .678 would be a legitimate entry. Place your UPPER limit, rounded to 3 decimal
places, in the second blank Correct.478
. For example, .789 would be a legitimate entry.
Answer Key: .
Question 5 of 20
1.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
Senior management of a consulting services firm is concerned
about a growing decline in the firm’s weekly number of billable hours. The firm
expects each professional employee to spend at least 40 hours per week on work.
In an effort to understand this problem better, management would like to
estimate the standard deviation of the number of hours their employees spend on
work-related activities in a typical week. Rather than reviewing the records of
all the firm’s full-time employees, the management randomly selected a sample
of size 51 from the available frame. The sample mean and sample standard
deviations were 48.5 and 7.5 hours, respectively.
Construct a 95% confidence interval for the standard
deviation of the number of hours this firm’s employees spend on work-related
activities in a typical week.
Place your LOWER limit, in hours, rounded to 1 decimal
place, in the first blank. For example, 6.7 would be a legitimate entry. Correct6.3
Place your UPPER limit, in hours, rounded to 1 decimal
place, in the second blank. For example, 12.3 would be a legitimate entry. Correct9.3
Answer Key:
Question 6 of 20
1.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For scientific
notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
A marketing research consultant hired by Coca-Cola is
interested in determining the proportion of customers who favor Coke over other
soft drinks. A random sample of 400 consumers was selected from the market
under investigation and showed that 53% favored Coca-Cola over other brands.
Compute a 95% confidence interval for the true proportion of
people who favor Coke. Place your LOWER limit, rounded to 3 decimal places, in
the first blank Correct.481 . For
example, .345 would be a legitimate entry. Place your UPPER limit in the second
blank Correct.579 . For example, .456
would be a legitimate entry.
Answer Key:
Question 7 of 20
0.0/ 1.0 Points
Accepted characters: numbers, decimal point markers (period
or comma), sign indicators (-), spaces (e.g., as thousands separator, 5 000),
“E” or “e” (used in scientific notation). NOTE: For
scientific notation, a period MUST be used as the decimal point marker.
Complex numbers should be in the form (a + bi) where
“a” and “b” need to have explicitly stated values.
For example: {1+1i} is valid whereas {1+i} is not. {0+9i} is
valid whereas {9i} is not.
The personnel department of a large corporation wants to
estimate the family dental expenses of its employees to determine the feasibility
of providing a dental insurance plan. A random sample of 12 employees reveals
the following family dental expenses (in dollars): 115, 370, 250, 593, 540,
225, 177, 425, 318, 182, 275, and 228.
Construct a 90% confidence interval estimate for the standard
deviation of family dental expenses for all employees of this corporation.
Place your LOWER limit, in dollars rounded to 1 decimal
place, in the first blank. Do not use a dollar sign, a comma, or any other
stray mark. For example, 123.4 would be a legitimate entry. Correct231.5
Place your UPPER limit, in dollars rounded to 1 decimal
place, in the second blank. Do not use a dollar sign, a comma, or any other
stray mark. For example, 567.8 would be a legitimate entry. Correct384.9
Answer Key:
Part 2 of 3 – 10.0/
11.0 Points
Question 8 of 20
1.0/ 1.0 Points
In constructing a confidence interval estimate for a
population mean, when we replace f$sigma f$
with the sample standard deviation (s), we introduce a new source of
variability and the sampling distribution we use is:
A.F- distribution
B.the normal distribution
C.chi-square
distribution
Correct D.t
-distribution
Answer Key:
Question 9 of 20
1.0/ 1.0 Points
A food snack manufacturer samples 15 bags of pretzels off
the assembly line and weighed their contents. If the sample mean is 10.0 and
the sample standard deviation is 0.15, find the 95% confidence interval
estimate for the true mean.
A.(9.96, 10.04)
B.(9.68, 10.32)
C.(9.97, 10.80)
Correct D.(9.92,
10.08)
Answer Key:
Question 10 of 20
1.0/ 1.0 Points
In a study of elephants a researcher wishes to determine the
average weight of a certain subspecies of elephants. From previous studies, the
standard deviation of the weights of elephants in this subspecies is known to
be 1500 pounds. How many elephants does the researcher need to weigh so that he
can be 80% confident that the average weight of elephants in his sample is
within 350 pounds of the true average weight for this subspecies?
A.50
B.39
C.166
Correct
Answer Key:
Question 11 of 20
0.0/ 1.0 Points
If you increase the confidence level, the confidence
interval ____________.
A.stays the same
B.decreases
C.increases
Incorrect
D.may increase or decrease, depending on the sample data
Answer Key:
Question 12 of 20
1.0/ 1.0 Points
The average gas mileage of a certain model car is 26 miles
per gallon. If the gas mileages are normally distributed with a standard
deviation of 1.3, find the probability that a randomly selected car of this
model has a gas mileage between 25.8 and 26.3 miles per gallon.
Correct A.0.15
B.0.85
C.0.70
D.0.30
Answer Key:
Question 13 of 20
1.0/ 1.0 Points
At a large department store, the average number of years of
employment for a cashier is 5.7 with a standard deviation of 1.8 years. If the
number of years of employment at this department store is normally distributed,
what is the probability that a cashier selected at random has worked at the
store for over 10 years?
A.0.4916
B.0.9916
Correct C.0.0084
D.0.0054
Answer Key:
Question 14 of 20
1.0/ 1.0 Points
In order to be
accepted into a top university, applicants must score within the top 5% on the
SAT exam. Given that SAT test scores are normally distributed with a mean of
1000 and a standard deviation of 200, what is the lowest possible score a student
needs to qualify for acceptance into the university?
Correct A.1330
B.1400
C.1250
D.1100
Answer Key:
Question 15 of 20
1.0/ 1.0 Points
From a sample of 500 items, 30 were found to be defective.
The point estimate of the population proportion defective will be:
A.30
B.0.60
C.16.667
Correct D..06
Answer Key
Question 16 of 20
1.0/ 1.0 Points
The upper limit of the 90% confidence interval for the
population proportion p, given that n = 100; and f$hat{p}f$
= 0.20 is
A.0.4684
Correct B.0.2658
C.0.5316
D.0.7342
Answer Key
Question 17 of 20
1.0/ 1.0 Points
Which of the following will make a confidence interval
narrower and more precise?
A.Larger sample size
and higher confidence level
B.Smaller sample size
and lower confidence level
Correct C.Larger
sample size and lower confidence level
D.Smaller sample size
and higher confidence level
Answer Key
Question 18 of 20
1.0/ 1.0 Points
The t- distribution for developing a confidence interval for
a mean has _____ degrees of freedom.
A.n – 2
B.n + 1
Correct C.n – 1
D.n
Answer Key
Part 3 of 3 – 2.0/
2.0 Points
Question 19 of 20
1.0/ 1.0 Points
The lower limit of the 95% confidence interval for the
population proportion p, given that n = 300; and f$hat{p}f$
= 0.10 is 0.1339.
Correct
True
False
Answer Key:
Question 20 of 20
1.0/ 1.0 Points
The upper limit of the 90% confidence interval for the
population proportion p, given that n = 100; and f$hat{p}f$ = 0.20 is 0.2341.
Correct
True
False
Answer Key
