Exam 9: Statistical Inferences Based on Two Samples

A car insurance company would like to determine the proportion of accident claims covered by the company.According to a preliminary estimate 60% of the claims are covered.How large a sample should be taken to estimate the proportion of accident claims covered by the company if we want to be 98% confident that the sample percentage is within 3% of the actual percentage of the accidents covered by the insurance company?

(Essay)

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Question 21

The manager of a grocery store wants is interested in the average amount of water contained in a "1L" bottle purchased from a known manufacturer.It is known from the manufacturer's specifications that the amount of water is normally distributed with a standard deviation of 0.02L.A random sample of 32 bottles is selected,and the mean amount of water per 1L bottle is found to be 0.995L.The 99.9% confidence interval for the mean water content is _____.

(Multiple Choice)

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Question 22

A sample of 2,000 people yielded $\hat { p }$ =.52. -Calculate a 95 percent confidence interval for p.

(Essay)

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Question 23

In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a variance of 0.09.Assuming bolt length is normally distributed,what is the 90% confidence interval for the true mean length of the bolt?

(Multiple Choice)

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Question 24

The weight of a product is normally distributed.A sample of 50 units is taken from a batch.The sample yielded the following results: $\bar { x }$ = 75kg and s = 10kg. -Calculate a 90 percent confidence interval for $\mu$ .

(Essay)

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Question 25

A sample of 8 items has an average fat content of 18.6 grams and a standard deviation of 2.4 grams.Assuming fat content has a normal distribution,construct a 99 percent confidence interval for $\mu$ .

(Essay)

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Question 26

An insurance company estimates 40 percent of its claims have errors.The insurance company wants to estimate with 90 percent confidence the proportion of claims with errors.What sample size is needed if they wish to be within 5 percent of the actual?

(Essay)

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Question 27

Suppose we are interested in the population mean of a normally distributed population with unknown standard deviation.If we take a sample of 12 observations from this population,the confidence interval for the population mean is computed based on the t distribution.

(True/False)

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Question 28

In a randomly selected group of 650 automobile deaths,180 were alcohol related.Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

(Essay)

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Question 29

When the level of confidence and standard deviation remain the same,a confidence interval for a population mean based on a sample of n = 100 will be narrower than a confidence interval for a population mean based on a sample of n = 50.

(True/False)

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Question 30

A wine manufacturer is concerned about the percentage of alcohol in each bottle.A random sample of 31 bottles is tested.The average alcohol percentage is 12.58% and the standard deviation is 0.25%.If wine content is normally distributed,the 90% confidence interval for the average wine content is _____.

(Multiple Choice)

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Question 31

A psychologist has designed a new intelligence test.Historically,time to complete the old test was normally distributed with a standard deviation of 5 minutes.A sample of 50 new test taking times yielded an average time of 118 minutes.The 99% confidence interval for the average test taking time is _____.

(Multiple Choice)

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Question 32

To investigate the satisfaction level with garbage removal in an urban area,a telephone survey was taken of 100 residents.Seven residents reported being satisfied with their garbage removal.A 90% confidence interval for the true percentage of all satisfied residents would be _____.

(Multiple Choice)

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Question 33

What is a 95 percent confidence interval for $\mu$ when n = 10, $\bar { x }$ = 35.6,and s = 13.0? Assume population normality.

(Essay)

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Question 34

Of a random sample of 600 trucks at a bridge,114 had bad signal lights.Construct a 95 percent confidence interval for the percentage of trucks that had bad signal lights.

(Essay)

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Question 35

In a study of factors affecting job satisfaction,320 employed individuals were measured for an index of satisfaction and the sample mean was 28.8 and the sample standard deviation was 7.3.Following,the 98% confidence interval for the population mean would be _____.

(Multiple Choice)

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Question 36

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.If seedling height is normally distributed,the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected would be _____.

(Multiple Choice)

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Question 37

When the level of confidence and sample size remain the same,a confidence interval for a population proportion p will be narrower when $\hat { p } ( 1 - \hat { p } )$ is larger than when $\hat { p } ( 1 - \hat { p } )$ is smaller.

(True/False)

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Question 38

The weight of an empty cereal box is normally distributed with a standard deviation of 2 grams.You obtain a sample of 20 boxes with a mean weight of 16 grams.The confidence interval for the average weight is based on the _____ distribution.

(Short Answer)

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Question 39

An experiment was conducted to determine the effectiveness of a method designed to remove oil wastes found in soil.Three contaminated soil samples were treated.After 95 days,the percentage of contamination removed from each soil sample was measured with a mean of 49.3% and a standard deviation of 1.5%.Assume the percentage of contamination is normally distributed.If we wished to narrow the boundary around μ for a 98% confidence interval to within 0.5%,how many soil samples should be in our experiment?

(Multiple Choice)

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Question 40

Showing 21 - 40 of 168

A sample of 2,000 people yielded $\hat { p }$ =.52. -Calculate a 95 percent confidence interval for p.

In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a variance of 0.09.Assuming bolt length is normally distributed,what is the 90% confidence interval for the true mean length of the bolt?

The weight of a product is normally distributed.A sample of 50 units is taken from a batch.The sample yielded the following results: $\bar { x }$ = 75kg and s = 10kg. -Calculate a 90 percent confidence interval for $\mu$ .

A sample of 8 items has an average fat content of 18.6 grams and a standard deviation of 2.4 grams.Assuming fat content has a normal distribution,construct a 99 percent confidence interval for $\mu$ .

An insurance company estimates 40 percent of its claims have errors.The insurance company wants to estimate with 90 percent confidence the proportion of claims with errors.What sample size is needed if they wish to be within 5 percent of the actual?

Suppose we are interested in the population mean of a normally distributed population with unknown standard deviation.If we take a sample of 12 observations from this population,the confidence interval for the population mean is computed based on the t distribution.

In a randomly selected group of 650 automobile deaths,180 were alcohol related.Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

When the level of confidence and standard deviation remain the same,a confidence interval for a population mean based on a sample of n = 100 will be narrower than a confidence interval for a population mean based on a sample of n = 50.

To investigate the satisfaction level with garbage removal in an urban area,a telephone survey was taken of 100 residents.Seven residents reported being satisfied with their garbage removal.A 90% confidence interval for the true percentage of all satisfied residents would be _____.

What is a 95 percent confidence interval for $\mu$ when n = 10, $\bar { x }$ = 35.6,and s = 13.0? Assume population normality.

Of a random sample of 600 trucks at a bridge,114 had bad signal lights.Construct a 95 percent confidence interval for the percentage of trucks that had bad signal lights.

In a study of factors affecting job satisfaction,320 employed individuals were measured for an index of satisfaction and the sample mean was 28.8 and the sample standard deviation was 7.3.Following,the 98% confidence interval for the population mean would be _____.

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.If seedling height is normally distributed,the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected would be _____.

When the level of confidence and sample size remain the same,a confidence interval for a population proportion p will be narrower when $\hat { p } ( 1 - \hat { p } )$ is larger than when $\hat { p } ( 1 - \hat { p } )$ is smaller.

The weight of an empty cereal box is normally distributed with a standard deviation of 2 grams.You obtain a sample of 20 boxes with a mean weight of 16 grams.The confidence interval for the average weight is based on the _____ distribution.

An Introduction to Business Statistics

Descriptive Statistics

Probability

Discrete Random Variables

Continuous Random Variables

Sampling Distributions

Confidence Intervals

Hypothesis Testing

Experimental Design and Analysis of Variance

Correlation Coefficient and Simple Linear Regression Analysis

Multiple Regression and Model Building

Nonparametric Methods

Chi-Square Tests

Decision Theory

Time Series Forecasting

Filters

Exam 9: Statistical Inferences Based on Two Samples

A sample of 2,000 people yielded p^\hat { p }p^​ =.52. -Calculate a 95 percent confidence interval for p.

In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a variance of 0.09.Assuming bolt length is normally distributed,what is the 90% confidence interval for the true mean length of the bolt?

The weight of a product is normally distributed.A sample of 50 units is taken from a batch.The sample yielded the following results: xˉ\bar { x }xˉ = 75kg and s = 10kg. -Calculate a 90 percent confidence interval for μ\muμ .

A sample of 8 items has an average fat content of 18.6 grams and a standard deviation of 2.4 grams.Assuming fat content has a normal distribution,construct a 99 percent confidence interval for μ\muμ .

An insurance company estimates 40 percent of its claims have errors.The insurance company wants to estimate with 90 percent confidence the proportion of claims with errors.What sample size is needed if they wish to be within 5 percent of the actual?

Suppose we are interested in the population mean of a normally distributed population with unknown standard deviation.If we take a sample of 12 observations from this population,the confidence interval for the population mean is computed based on the t distribution.

In a randomly selected group of 650 automobile deaths,180 were alcohol related.Construct a 95 percent confidence interval for the true proportion of all automobile accidents caused by alcohol.

When the level of confidence and standard deviation remain the same,a confidence interval for a population mean based on a sample of n = 100 will be narrower than a confidence interval for a population mean based on a sample of n = 50.

To investigate the satisfaction level with garbage removal in an urban area,a telephone survey was taken of 100 residents.Seven residents reported being satisfied with their garbage removal.A 90% confidence interval for the true percentage of all satisfied residents would be _____.

What is a 95 percent confidence interval for μ\muμ when n = 10, xˉ\bar { x }xˉ = 35.6,and s = 13.0? Assume population normality.

Of a random sample of 600 trucks at a bridge,114 had bad signal lights.Construct a 95 percent confidence interval for the percentage of trucks that had bad signal lights.

In a study of factors affecting job satisfaction,320 employed individuals were measured for an index of satisfaction and the sample mean was 28.8 and the sample standard deviation was 7.3.Following,the 98% confidence interval for the population mean would be _____.

A botanist measures the heights of 16 seedlings and obtains a mean and standard deviation of 72.5 cm and 4.5 cm,respectively.If seedling height is normally distributed,the 95% confidence interval for the mean height of seedlings in the population form which the sample was selected would be _____.

When the level of confidence and sample size remain the same,a confidence interval for a population proportion p will be narrower when p^(1−p^)\hat { p } ( 1 - \hat { p } )p^​(1−p^​) is larger than when p^(1−p^)\hat { p } ( 1 - \hat { p } )p^​(1−p^​) is smaller.

The weight of an empty cereal box is normally distributed with a standard deviation of 2 grams.You obtain a sample of 20 boxes with a mean weight of 16 grams.The confidence interval for the average weight is based on the _____ distribution.

An Introduction to Business Statistics

Descriptive Statistics

Probability

Discrete Random Variables

Continuous Random Variables

Sampling Distributions

Confidence Intervals

Hypothesis Testing

Experimental Design and Analysis of Variance

Correlation Coefficient and Simple Linear Regression Analysis

Multiple Regression and Model Building

Nonparametric Methods

Chi-Square Tests

Decision Theory

Time Series Forecasting

Filters

A sample of 2,000 people yielded $\hat { p }$ =.52. -Calculate a 95 percent confidence interval for p.

The weight of a product is normally distributed.A sample of 50 units is taken from a batch.The sample yielded the following results: $\bar { x }$ = 75kg and s = 10kg. -Calculate a 90 percent confidence interval for $\mu$ .

A sample of 8 items has an average fat content of 18.6 grams and a standard deviation of 2.4 grams.Assuming fat content has a normal distribution,construct a 99 percent confidence interval for $\mu$ .

What is a 95 percent confidence interval for $\mu$ when n = 10, $\bar { x }$ = 35.6,and s = 13.0? Assume population normality.

When the level of confidence and sample size remain the same,a confidence interval for a population proportion p will be narrower when $\hat { p } ( 1 - \hat { p } )$ is larger than when $\hat { p } ( 1 - \hat { p } )$ is smaller.