Exam 9: Estimation From Sample Data

The office manager for an ophthalmologist wants to estimate the average time that the doctor spends with each patient in order to better schedule appointments.A random sample of 49 is taken and the sample mean is 20.3 minutes.Assume that the office manager knows from past experience that the standard deviation is 14 minutes.She finds that a 95% confidence interval is between 18.3 and 22.3 minutes. What is the point estimate of the population mean? What is the confidence coefficient?

(Short Answer)

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Question 21

A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25.The upper limit of a 95% confidence interval for the population mean would equal:

(Multiple Choice)

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Question 22

Since the t-interval is often associated with interval estimates based on small samples,it is not appropriate for large samples.

(True/False)

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Question 23

If a sample containing 20 observations is taken from a normally distributed population and a 90% confidence estimate for $\mu$ is needed,the appropriate t-score is:

(Multiple Choice)

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Question 24

Which of the following is not a part of the formula for constructing a confidence interval estimate of the population mean?

(Multiple Choice)

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Question 25

Thirty-six months were randomly sampled and the discount rate on new issues of 91-day Treasury Bills was collected.The sample mean is 4.76% and the standard deviation is 171.21.What is the unbiased estimate for the mean of the population?

(Multiple Choice)

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Question 26

A college basketball player has been keeping track of his free throw shooting practice over the summer.Each day that he practices,he shoots 150 free throws and counts the number he makes.Today he made 117 free throws.What is the 95% confidence interval around this sample?

(Essay)

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Question 27

An economics professor is taping 60-minute lectures for replay over the university radio station.To make sure that the brand of tapes that will be used records for at least sixty minutes,one dozen are purchased and examined to determine if they do record for sixty minutes.The results of the recording test in minutes show a mean of 61.28 and standard deviation of 3.868.The professor assumes that the playing time is normally distributed.Construct an 80-percent confidence interval for the mean recording time employing these data. to

(Short Answer)

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Question 28

From a sample of 400 people who were asked if they were in favor of a proposition to ban smoking in restaurants,320 responded yes.Develop a 98% confidence interval using this sample.

(Short Answer)

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Question 29

In developing an interval estimate for a population mean,the population standard deviation $\text { ? }$ was assumed to be 10.The interval estimate was 50.92 $\pm$ 2.14.Had $\text { ? }$ equaled 20,the interval estimate would be:

(Multiple Choice)

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Question 30

Determine the limits of the 90% confidence interval for $\mu$ ,given that n = 144; $\bar { x }$ = 7; and $\text { σ }$ = 2. to

(Short Answer)

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Question 31

A sample of 200 light bulbs was tested and it was found that 11 were defective.Calculate a 95% confidence interval around this sample proportion.

(Multiple Choice)

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Question 32

The t distribution is used to calculate a confidence interval when the population is normally distributed and the population standard deviation is known.

(True/False)

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Question 33

An auditor wishes to take a sample to verify the accounts receivable balances for a company having 500 accounts.From past history,he knows that $\text { σ }$ is $102.49.What sample size must be taken to be 99% confident that the estimate will be within $10 of the true mean account balance?

(Short Answer)

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Question 34

If a sample containing 30 observations is taken from a normally distributed population and a 98% confidence estimate for $\mu$ is needed,the appropriate t-score is:

(Multiple Choice)

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Question 35

An estimator is unbiased if the expected value of the sample statistic is the same as the actual value of the population parameter it is intended to estimate.

(True/False)

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Question 36

A proponent of private aid to assist those who are suffering from hunger has decided to take a random sample to estimate the average annual contribution in her community to world hunger relief.A similar study in a comparable community reported the standard deviation of giving as $15.Our proponent believes that her estimate $\bar { x }$ should be within $3 of the true average and with 92-percent confidence.If 1222 in this community contribute to world hunger relief,what size sample is appropriate?

(Short Answer)

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Question 37

As marketing manager for a very large discount building supply,you wish to know what proportion of your city's population conducted do-it-yourself home improvement projects during the past year.The national percentage is 62%; therefore,you decide to use this value in estimating sample size for a study to achieve 90% confidence with the estimate no more than 5% from the true proportion.What is the appropriate sample size?

(Short Answer)

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Question 38

What is a confidence interval?

(Essay)

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Question 39

An unbiased estimator is:

(Multiple Choice)

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Question 40

Showing 21 - 40 of 150

A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25.The upper limit of a 95% confidence interval for the population mean would equal:

Since the t-interval is often associated with interval estimates based on small samples,it is not appropriate for large samples.

If a sample containing 20 observations is taken from a normally distributed population and a 90% confidence estimate for $\mu$ is needed,the appropriate t-score is:

Which of the following is not a part of the formula for constructing a confidence interval estimate of the population mean?

Thirty-six months were randomly sampled and the discount rate on new issues of 91-day Treasury Bills was collected.The sample mean is 4.76% and the standard deviation is 171.21.What is the unbiased estimate for the mean of the population?

A college basketball player has been keeping track of his free throw shooting practice over the summer.Each day that he practices,he shoots 150 free throws and counts the number he makes.Today he made 117 free throws.What is the 95% confidence interval around this sample?

From a sample of 400 people who were asked if they were in favor of a proposition to ban smoking in restaurants,320 responded yes.Develop a 98% confidence interval using this sample.

In developing an interval estimate for a population mean,the population standard deviation $\text { ? }$ was assumed to be 10.The interval estimate was 50.92 $\pm$ 2.14.Had $\text { ? }$ equaled 20,the interval estimate would be:

Determine the limits of the 90% confidence interval for $\mu$ ,given that n = 144; $\bar { x }$ = 7; and $\text { σ }$ = 2. to

A sample of 200 light bulbs was tested and it was found that 11 were defective.Calculate a 95% confidence interval around this sample proportion.

The t distribution is used to calculate a confidence interval when the population is normally distributed and the population standard deviation is known.

An auditor wishes to take a sample to verify the accounts receivable balances for a company having 500 accounts.From past history,he knows that $\text { σ }$ is $102.49.What sample size must be taken to be 99% confident that the estimate will be within $10 of the true mean account balance?

If a sample containing 30 observations is taken from a normally distributed population and a 98% confidence estimate for $\mu$ is needed,the appropriate t-score is:

An estimator is unbiased if the expected value of the sample statistic is the same as the actual value of the population parameter it is intended to estimate.

What is a confidence interval?

An unbiased estimator is:

A Preview of Business Statistics

Visual Description of Data

Statistical Description of Data

Data Collection and Sampling Methods

Probability: Review of Basic Concepts

Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions

Hypothesis Tests Involving a Sample Mean or Proportion

Hypothesis Tests Involving Two Sample Means

Analysis of Variance Tests

Chi-Square Applications

Nonparametric Methods

Simple Linear Regression and Correlation

Multiple Regression and Correlation

Model Building

Models for Time Series and Forecasting

Decision Theory

Total Quality Management

Filters

Exam 9: Estimation From Sample Data

A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25.The upper limit of a 95% confidence interval for the population mean would equal:

Since the t-interval is often associated with interval estimates based on small samples,it is not appropriate for large samples.

If a sample containing 20 observations is taken from a normally distributed population and a 90% confidence estimate for μ\muμ is needed,the appropriate t-score is:

Which of the following is not a part of the formula for constructing a confidence interval estimate of the population mean?

Thirty-six months were randomly sampled and the discount rate on new issues of 91-day Treasury Bills was collected.The sample mean is 4.76% and the standard deviation is 171.21.What is the unbiased estimate for the mean of the population?

A college basketball player has been keeping track of his free throw shooting practice over the summer.Each day that he practices,he shoots 150 free throws and counts the number he makes.Today he made 117 free throws.What is the 95% confidence interval around this sample?

From a sample of 400 people who were asked if they were in favor of a proposition to ban smoking in restaurants,320 responded yes.Develop a 98% confidence interval using this sample.

In developing an interval estimate for a population mean,the population standard deviation ? \text { ? } ? was assumed to be 10.The interval estimate was 50.92 ±\pm± 2.14.Had ? \text { ? } ? equaled 20,the interval estimate would be:

Determine the limits of the 90% confidence interval for μ\muμ ,given that n = 144; xˉ\bar { x }xˉ = 7; and σ \text { σ } σ = 2. ____________________ to ____________________

A sample of 200 light bulbs was tested and it was found that 11 were defective.Calculate a 95% confidence interval around this sample proportion.

The t distribution is used to calculate a confidence interval when the population is normally distributed and the population standard deviation is known.

An auditor wishes to take a sample to verify the accounts receivable balances for a company having 500 accounts.From past history,he knows that σ \text { σ } σ is $102.49.What sample size must be taken to be 99% confident that the estimate will be within $10 of the true mean account balance?

If a sample containing 30 observations is taken from a normally distributed population and a 98% confidence estimate for μ\muμ is needed,the appropriate t-score is:

An estimator is unbiased if the expected value of the sample statistic is the same as the actual value of the population parameter it is intended to estimate.

What is a confidence interval?

An unbiased estimator is:

A Preview of Business Statistics

Visual Description of Data

Statistical Description of Data

Data Collection and Sampling Methods

Probability: Review of Basic Concepts

Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions

Hypothesis Tests Involving a Sample Mean or Proportion

Hypothesis Tests Involving Two Sample Means

Analysis of Variance Tests

Chi-Square Applications

Nonparametric Methods

Simple Linear Regression and Correlation

Multiple Regression and Correlation

Model Building

Models for Time Series and Forecasting

Decision Theory

Total Quality Management

Filters

If a sample containing 20 observations is taken from a normally distributed population and a 90% confidence estimate for $\mu$ is needed,the appropriate t-score is:

In developing an interval estimate for a population mean,the population standard deviation $\text { ? }$ was assumed to be 10.The interval estimate was 50.92 $\pm$ 2.14.Had $\text { ? }$ equaled 20,the interval estimate would be:

Determine the limits of the 90% confidence interval for $\mu$ ,given that n = 144; $\bar { x }$ = 7; and $\text { σ }$ = 2. to

An auditor wishes to take a sample to verify the accounts receivable balances for a company having 500 accounts.From past history,he knows that $\text { σ }$ is $102.49.What sample size must be taken to be 99% confident that the estimate will be within $10 of the true mean account balance?

If a sample containing 30 observations is taken from a normally distributed population and a 98% confidence estimate for $\mu$ is needed,the appropriate t-score is: