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Exam 7: Estimation: Single Population

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Question 1

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If a sample of size 200 has 40 successes,the lower limit of a confidence interval at the 95% level of confidence for the population proportion is:

A) 0.2554
B) 0.1446
C) 0.2465
D) 0.1535

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Question 2

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THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A clinic offers a weight-reduction program.A review of its records revealed the following weight losses,in pounds,for a random sample of 10 of its clients at the conclusion of the program: 20,15,21,28,22,19,9,14,18,and 23. -Find a 95% confidence interval for the population mean.

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n = 10,
= 18.9,s = 5.03,t _9,0.025 =...

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Question 3

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A 95% confidence interval for the population proportion will not extend approximately 1.96 on each side of the sample proportion.

If a sample of size 61 is selected,the value of A for the probability P(-A ≤ t ≤A) = 0.95 is:

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The Daytona Beach Tourism Commission is interested in the average amount of money a typical college student spends per day during spring break.They survey 35 students and find that the mean spending is $63.57 with a standard deviation of $17.32. -What level of confidence is associated with an interval of $58.62 to $68.52 for the population mean daily spending?

A sample statistic such that the mean of all its possible values equals the population parameter the statistic seeks to estimate is an unbiased estimator.

A sample of 50 students is taken from Utah Valley University (UVU) .These students spent an average of $175 on books this semester,with a standard deviation of $25.A 95% confidence interval for the average amount of money spent on books for all students at UVU is equal to ________.(Hint: Use Excel function to obtain the critical value. )

Find the upper confidence limit of the 90% confidence interval.

Which of the following statements is true regarding the width of a confidence interval for a population proportion?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A researcher is interested in determining the percentage of all households in the U.S.that have more than one home computer.In a survey of 492 households,27% indicated that they own more than one home computer. -The researcher reports a confidence interval of 0.2312 to 0.3096 but neglects to tell you the confidence level.What is the confidence level associated with this interval?

For a 90% confidence interval,the reliability factor is equal to 1.96.

In a recent survey of 574 employees,15.5% indicated that they were not in favor of a particular plan.What is the level of confidence associated with the interval of 12.85% to 19.89%?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A regional CPA firm conducted an audit for a discount chain.One part of the audit involved developing an estimate for the mean dollar error in total charges that occur during the checkout process.They wish to develop a 90% confidence interval estimate for the population mean.A simple random sample of n = 20 is selected,with the following data (in dollars): -Calculate the sample standard deviation.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: Suppose that the waiting times for patients at a local hospital are normally distributed with known population standard deviation of 30 minutes.A random sample of 75 patients in the local hospital had a mean time of 90 minutes.Assume a 95% confidence interval for the population mean μ. -Calculate the margin of error of the 95% confidence interval.

The t-distribution with n -1 degrees of freedom is often used to construct confidence intervals of the population mean when the population standard deviation is known.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A random sample of ten homes in a particular suburb had the following selling prices (in thousands of dollars): 92,83,110,115,108,96,102,90,100,and 98. -Find a point estimate of the population mean that is unbiased and efficient.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A school bus driver records the time (in minutes) it takes to commute to school for six days.Those results are: 25,22,17,20,15,and 10.Assuming the population is normally distributed,develop a 90% confidence interval for the population mean. -Determine the reliability factor from the Student's t distribution table.

Let X₁,X₂,X₃,and X₄ be a random sample of observations from a population with mean μ and variance σ².Consider the following estimator of μ: ₁ = 0.15 X₁ + 0.35 X₂ + 0.20 X₃ + 0.30 X₄.What is the variance of ₁?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The number of beverage cans produced each hour from a vending machine is normally distributed with a standard deviation of 8.6.For a random sample of 12 hours,the average number of beverage cans produced was 326.0.Assume a 99% confidence interval for the population mean number of beverage cans produced per hour. -Calculate the margin of error of the 99% confidence interval.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A clinic offers a weight-reduction program.A review of its records revealed the following weight losses,in pounds,for a random sample of 10 of its clients at the conclusion of the program: 20,15,21,28,22,19,9,14,18,and 23. -How large the sample is needed to estimate the population proportion if ME = 0.09,a = 0.05?