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. 

Assume 50 random samples of the same sample size are taken from a population, and a 90% confidence interval is constructed from each sample. How many of the intervals would you expect to contain the true population mean? 

Answer: 
  Round your answer to a whole number value as necessary.  For example, 37 would be a legitimate 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 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. 
  

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 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. 

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 24.6 mpg and a standard deviation of 11.2 mpg.  If 30 such cars are tested, what is the probability the average mpg achieved by these 30 cars will be greater than 27? 

Answer:   
   Round your answer to 4 decimal places as necessary.  For example, 0.1357 would be a legitimate entry. 

Question 4 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. 

A lawyer researched the average number of years served by 45 different justices on the Supreme Court. The average number of years served was 13.8 years with a standard deviation of 7.3 years. What is the 95% confidence interval estimate for the average number of years served by all Supreme Court justices? Place your limits,rounded to 1 decimal place, in the blanks. Place you lower limit in the first blank.    Place your upper limit in the second blank.    When entering your answer do not use any labels or symbols. Simply provide the numerical value. For example, 12.3 would be a legitimate entry. 

Question 5 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. 

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. 
  

Place your UPPER limit, in hours, rounded to 1 decimal place, in the second blank. For example, 12.3 would be a legitimate entry. 
  

Question 6 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 percent defective for parts produced by a manufacturing process is targeted at 4%. The process is monitored daily by taking samples of sizes n = 160 units. Suppose that today’s sample contains 14 defectives. 

Determine a 95% confidence interval for the proportion defective for the process today. 

Place your LOWER limit, rounded to 3 decimal places, in the first blank. For example, 0.123 would be a legitimate answer. 
  

Place your UPPER limit, rounded to 3 decimal places, in the second blank. For example, 0.345 would be a legitimate entry. 
  

Question 7 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. 

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 σ=$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. 

Part 2 of 3 -

 

Question 8 of 20

1.0 Points

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

 

 

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

 

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

 

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

 

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

 

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Question 9 of 20

1.0 Points

Compute  P(  t15  2.0) where t15 has a t-distribution with 15 degrees of freedom.

 

 

  A.0.93606

 

  B.0.96803

 

  C.0.7639

 

  D.0.03197

 

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Question 10 of 20

1.0 Points

Which of the following will make a confidence interval narrower and more precise?

 

 

  A.Larger sample size and lower confidence level

 

  B.Smaller sample size and higher confidence level

 

  C.Smaller sample size and lower confidence level

 

  D.Larger sample size and higher confidence level

 

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Question 11 of 20

1.0 Points

A previous study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. How many nickels does a coin counter manufacturer need to weigh so that she can be 98% confident that her sample mean is within 25 milligrams of the true average weight of a nickel?

 

 

  A.36

 

  B.196

 

  C.239

 

  D.139

 

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Question 12 of 20

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The upper limit of the 90% confidence interval for the population proportion p, given that n = 100; and p^  = 0.20 is

 

 

  A.0.4684

 

  B.0.2658

 

  C.0.7342

 

  D.0.5316

 

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Question 13 of 20

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.

 

 

  A.0.15

 

  B.0.85

 

  C.0.70

 

  D.0.30

 

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Question 14 of 20

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..06

 

  B.30

 

  C.16.667

 

  D.0.60

 

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Question 15 of 20

1.0 Points

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

 

 

  A.decreases

 

  B.increases

 

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

 

  D.stays the same

 

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Question 16 of 20

1.0 Points

In constructing a confidence interval estimate for a population mean, when we replace σ  with the sample standard deviation (s), we introduce a new source of variability and the sampling distribution we use is:

 

 

  A.t -distribution

 

  B.F- distribution

 

  C.the normal distribution

 

  D.chi-square distribution

 

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Question 17 of 20

1.0 Points

A researcher wishes to know, with 98% confidence, the percentage of women who wear shoes that are too small for their feet. A previous study conducted by the Academy of Orthopedic Surgeons found that 80% of women wear shoes that are too small for their feet. If the researcher wants her estimate to be within 3% of the true proportion, how large a sample is necessary?

 

 

  A.966

 

  B.683

 

  C.183

 

  D.484

 

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Question 18 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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Part 3 of 3 -

 

Question 19 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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Question 20 of 20

1.0 Points

The 95% confidence interval for the population mean μ , given that the sample size n = 49 and the

                                                                 _

population standard deviation σ = 7, is x +1.96

                             __

 

 

  True

  False

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