Exam 10: Confidence Intervals

A researcher is interested in estimating the mean weight of a semi-tracker truck to determine the potential load capacity. She takes a random sample of 17 trucks and computes a sample mean of 20,000 pounds with sample standard deviation of 1,500. The 95% confidence interval for the population mean weight of a semi-tracker truck is ___.

(Multiple Choice)

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Question 21

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The 90% confidence interval for the population proportion is ___.

(Multiple Choice)

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Question 22

A researcher wants to estimate the percent of the population that uses the internet to stay informed on world news issues. The researcher wants to estimate the population proportion with a 98% level of confidence. He estimates from previous studies that at least 65% of the population stay informed on world issues through the internet. He also wants the error to be no more than.03. The sample size should be at least ___.

(Multiple Choice)

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Question 23

Suppose a random sample of 16 is selected from a population with a normal distribution with a known population standard deviation σ of 10. Assume that the sample mean is 4.2. Based on a 90% confidence interval for the population mean, we can conclude that 0.1 is a plausible number for the population mean μ.

(True/False)

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Question 24

Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 45 randomly selected walk-in customers, and calculated that their mean waiting time was 15 minutes. If Brian concludes that the average waiting time for all walk-in customers is 15 minutes, he is using a ___.

(Multiple Choice)

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Question 25

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The point estimate for this population proportion is ___.

(Multiple Choice)

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Question 26

If the standard deviation is known, the z distribution values may not be used to determine interval estimates for the population mean when

(Multiple Choice)

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Question 27

Suppose you want to construct a 98% confidence interval for the mean amount spent on entertainment by first-year university students. If the margin of error is not more than $2.00 and the population standard deviation is $30, determine the least sample size required to construct the confidence interval.

(Essay)

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Question 28

The z value associated with a two-sided 99% confidence interval is ___.

(Multiple Choice)

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Question 29

A market researcher computed a confidence interval for a population proportion using a 95% confidence level. Her boss decided that she wanted a 99% confidence level instead. The new interval with 99% confidence level will be wider than the original one with a 95% confidence level.

(True/False)

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Question 30

The employees of Cybertronics Inc. need to complete a certification online. A random sample of 16 employees gives an average time for completion of all the coursework and passing the tests of 20 hours. The population standard deviation is unknown but the sample standard deviation is 6 hours. You can assume that the population of employees is fairly large. Construct a 95% confidence interval for the average time required to complete the certification.

(Multiple Choice)

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Question 31

An assumption underlying the use of t statistic in sample-based estimation is that the population is normally distributed.

(True/False)

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Question 32

Before giving a standardized exam to a very large group of students, a professor tested it on a sample of 90 students, 50 of whom achieved an acceptable standard. If the professor wants to generalize the results to all students who will take the exam, compute a 95% confidence interval for the proportion of students who will likely meet an acceptable standard.

(Short Answer)

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Question 33

A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 800 is taken resulting in 360 items which possess the characteristic. The point estimate for this population proportion is ___.

(Multiple Choice)

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Question 34

To construct a confidence interval we first choose

(Multiple Choice)

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Question 35

The z value associated with a two?sided 80% confidence interval is ___.

(Multiple Choice)

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Question 36

The normal distribution is used to test about a population mean for large samples if the population standard deviation is known. "Large" is usually defined as ___.

(Multiple Choice)

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Question 37

A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The range of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should be at least ___.

(Multiple Choice)

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Question 38

When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.

(True/False)

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Question 39

In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the z distribution.

(True/False)

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Question 40

Showing 21 - 40 of 82

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The 90% confidence interval for the population proportion is ___.

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The point estimate for this population proportion is ___.

If the standard deviation is known, the z distribution values may not be used to determine interval estimates for the population mean when

The z value associated with a two-sided 99% confidence interval is ___.

A market researcher computed a confidence interval for a population proportion using a 95% confidence level. Her boss decided that she wanted a 99% confidence level instead. The new interval with 99% confidence level will be wider than the original one with a 95% confidence level.

An assumption underlying the use of t statistic in sample-based estimation is that the population is normally distributed.

A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 800 is taken resulting in 360 items which possess the characteristic. The point estimate for this population proportion is ___.

To construct a confidence interval we first choose

The z value associated with a two?sided 80% confidence interval is ___.

The normal distribution is used to test about a population mean for large samples if the population standard deviation is known. "Large" is usually defined as ___.

A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The range of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should be at least ___.

When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.

In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the z distribution.

Introduction to Statistics

Organizing and Visualizing Data

Descriptive Statistics

Gathering Data

Probability

Decision Analysis and Expected Value

Discrete Probability Distributions

Continuous Distributions

Sampling Distributions

Hypothesis Testing for Single Populations

Hypothesis Testing for Two Populations

Analysis of Variance Anova

Linear Correlation and Simple Linear Regression Analysis

Categorical Versus Categorical: Tests

Filters

Exam 10: Confidence Intervals

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were not \textbf{ not } not business related. The 90% confidence interval for the population proportion is ___.

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were not \textbf{ not } not business related. The point estimate for this population proportion is ___.

If the standard deviation is known, the z distribution values may not be used to determine interval estimates for the population mean when

The z value associated with a two-sided 99% confidence interval is ___.

A market researcher computed a confidence interval for a population proportion using a 95% confidence level. Her boss decided that she wanted a 99% confidence level instead. The new interval with 99% confidence level will be wider than the original one with a 95% confidence level.

An assumption underlying the use of t statistic in sample-based estimation is that the population is normally distributed.

A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 800 is taken resulting in 360 items which possess the characteristic. The point estimate for this population proportion is ___.

To construct a confidence interval we first choose

The z value associated with a two?sided 80% confidence interval is ___.

The normal distribution is used to test about a population mean for large samples if the population standard deviation is known. "Large" is usually defined as ___.

A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The range of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should be at least ___.

When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.

In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the z distribution.

Introduction to Statistics

Organizing and Visualizing Data

Descriptive Statistics

Gathering Data

Probability

Decision Analysis and Expected Value

Discrete Probability Distributions

Continuous Distributions

Sampling Distributions

Hypothesis Testing for Single Populations

Hypothesis Testing for Two Populations

Analysis of Variance Anova

Linear Correlation and Simple Linear Regression Analysis

Categorical Versus Categorical: Tests

Filters

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The 90% confidence interval for the population proportion is ___.

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications. A random sample of 200 email messages was selected. Thirty of the messages were $\textbf{ not }$ business related. The point estimate for this population proportion is ___.