Question 1 of 20 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.

If a sample has 25 observations and a 99% confidence estimate for is needed, the appropriate value of the t-multiple required is _____________. Place your answer, rounded to 3 decimal places, in the blank. For example, 3.456 would be an appropriate entry.

Question 2 of 20 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: __________ Round your answer to 4 decimal places as necessary. For example, 0.1357 would be a legitimate entry.

Question 3 of 20 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.

If a sample has 20 observations and a 95% confidence estimate for is needed, the appropriate value of the t-multiple required is ___________ . Place your answer, rounded to 3 decimal places, in the blank. For example, 4.567 would be a legitimate entry.

Question 4 of 20 1.0 Points

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 ___________. For example, .678 would be a legitimate entry. Place your UPPER limit, rounded to 3 decimal places, in the second blank _________. For example, .789 would be a legitimate entry.

Question 5 of 20 1.0 Points

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 trying to estimate the average amount a family spends on food during a year. In the past, the standard deviation of the amount a family has spent on food during a year has been $1200. If you want to be 99% sure that you have estimated average family food expenditures within $60, how many families do you need to survey? Place your answer, a whole number, in the blank ______________ . For example, 1234 would be a legitimate entry.

Question 6 of 20 1.0 Points

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. ___________

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. _____________

Question 7 of 20 1.0 Points

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 _____________ . For example, .345 would be a legitimate entry. Place your UPPER limit in the second blank ____________. For example, .456 would be a legitimate entry.

Part 2 of 3 –

Question 8 of 20 1.0 Points

Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 26 pipes has a standard deviation of 10 inches.

A.14.0 < < 16.0

B.7.8 < < 13.8

C.74.0 < < 126.0

D.60.8 < < 190.5

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Question 9 of 20 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?

A.1330

B.1400

C.1250

D.1100

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Question 10 of 20 1.0 Points

A recent study of 750 Internet users in Europe found that 35% of Internet users were women. What is the 95% confidence interval estimate for the true proportion of women in Europe who use the Internet?

A.0.321 < p < 0.379

B.0.316 < p < 0.384

C.0.309 < p < 0.391

D.0.305 < p < 0.395

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Question 11 of 20 1.0 Points

Confidence intervals are a function of which of the following three things?

A.The data in the sample, the confidence level, and the sample size

B.The sampling distribution, the confidence level, and the degrees of freedom

C.The population, the sample, and the standard deviation

D.The sample, the variable of interest, and the degrees of freedom

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Question 12 of 20 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.166

B.50

C.39

D.31

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Question 13 of 20 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.Larger sample size and lower confidence level

C.Smaller sample size and lower confidence level

D.Smaller sample size and higher confidence level

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Question 14 of 20 1.0 Points

If you are constructing a confidence interval for a single mean, the confidence interval will___________ with an increase in the sample size.

A.stay the same

B.decrease

C.increase or decrease, depending on the sample data

D.increase

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Question 15 of 20 1.0 Points

A sample of 25 different payroll departments found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90% confidence interval for the average days worked by employees in all payroll departments?

A.301.0 < < 319.6

B.298.0 < < 322.6

C.302.2 < < 318.4

D.314.1 < < 316.8

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Question 16 of 20 1.0 Points

The t- distribution for developing a confidence interval for a mean has _____ degrees of freedom.

A.n + 1

B.n

C.n – 2

D.n – 1

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Question 17 of 20 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)

D.(9.92, 10.08)

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Question 18 of 20 1.0 Points

If you increase the confidence level, the confidence interval ____________.

A.increases

B.may increase or decrease, depending on the sample data

C.decreases

D.stays the same

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Part 3 of 3 –

Question 19 of 20 1.0 Points

The lower limit of the 95% confidence interval for the population proportion p, given that n = 300; and = 0.10 is 0.1339.

True

False

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Question 20 of 20 1.0 Points

A 90% confidence interval estimate for a population mean is determined to be 72.8 to 79.6. If the confidence level is reduced to 80%, the confidence interval becomes narrower.

True

False

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