Question 1

The chi-square distribution is:

Accepted Answer

A)  symmetric around zero. 
B)  positively skewed. 
C)  negatively skewed. 
D)  mound-shaped. 
A)  symmetric around zero. 
B)  positively skewed. 
C)  negatively skewed. 
D)  mound-shaped.

Question 2

After constructing a 95% confidence interval for a population mean μ, you decide that the interval is too wide to be of any value.To correct this problem, you need to:

Accepted Answer

A)  increase the population size. 
B)  increase the confidence level. 
C)  increase the sample mean. 
D)  increase the sample size. 
A)  increase the population size. 
B)  increase the confidence level. 
C)  increase the sample mean. 
D)  increase the sample size.

Question 3

To perform diagnostics on the consistency of a laboratory scale, multiple measurements are taken using a reference weight over the course of several days.The variance observed over 20 repeated measures is 248.What is a 99% confidence interval for the measurement variance of this scale?

Accepted Answer

A)  (122.129, 688.486) 
B)  (11.051, 26.239) 
C)  (117.809, 633.862) 
D)  (174.034, 413.213) 
A)  (122.129, 688.486) 
B)  (11.051, 26.239) 
C)  (117.809, 633.862) 
D)  (174.034, 413.213)

Question 4

A fire occurs in a massive warehouse used to store apples prior to shipment.The apples are held in individual crates.The insurance company wishes to estimate the proportion of crates that were damaged by smoke from the fire.How many crates should the insurance adjustor analyze if she wishes to construct a 98% confidence interval with a bound on the error of estimation of 0.02?

Accepted Answer

A)  3383 
B)  34 
C)  2401 
D)  4147 
A)  3383 
B)  34 
C)  2401 
D)  4147

Question 5

Researchers with the state Department of Natural Resources (DNR) wish to estimate the mean flow rate of water through a stream.From previous research conducted on similar streams, they know that the variance of flow rate is 27,556 gpm2.If the DNR researchers wish to create an interval that they are 99% confident will contain the mean flow rate with a bound on the error of estimation of 40 gpm, how many flow samples do they need?

Accepted Answer

A)  114 
B)  3,148,739 
C)  165 
D)  115 
A)  114 
B)  3,148,739 
C)  165 
D)  115

Question 6

The confidence level is the:

Accepted Answer

A)  probability that the confidence interval encloses the population parameter in repeated samplings. 
B)  confidence coefficient expressed as a percentage. 
C)  maximum level of confidence possible for a given point estimate to accurately predict an unknown parameter. 
D)  minimum (worst-case) level of confidence possible for a given point estimate to accurately predict an unknown parameter. 
A)  probability that the confidence interval encloses the population parameter in repeated samplings. 
B)  confidence coefficient expressed as a percentage. 
C)  maximum level of confidence possible for a given point estimate to accurately predict an unknown parameter. 
D)  minimum (worst-case) level of confidence possible for a given point estimate to accurately predict an unknown parameter.

Question 7

A random sample of 20 observations is selected from a normally distributed population.The sample variance is 12.In the 95% confidence interval for the population standard deviation, the upper limit will be:

Accepted Answer

A)  2.634. 
B)  2.750. 
C)  4.747. 
D)  5.060. 
A)  2.634. 
B)  2.750. 
C)  4.747. 
D)  5.060.

Question 8

Suppose we wish to estimate the proportion of classes skipped by seniors in a particular large class.How many samples should be drawn if we want a 90% confidence interval with a bound on the error of estimation of 3%?

Accepted Answer

A)  751 
B)  1068 
C)  752 
D)  1067 
A)  751 
B)  1068 
C)  752 
D)  1067

Question 9

In a study of typical student grade-point averages (GPAs), we sample 16 students and find an average GPA of 2.76, with a standard deviation of 0.48.Assuming the GPAs are normally distributed, what is an interval that we can be 80% certain contains the mean student GPA?

Accepted Answer

A)  (2.12, 3.40) 
B)  (2.61, 2.91) 
C)  (2.60, 2.92) 
D)  (2.66, 2.86) 
A)  (2.12, 3.40) 
B)  (2.61, 2.91) 
C)  (2.60, 2.92) 
D)  (2.66, 2.86)

Question 10

A shady operator wants to make sure the sample results are within the confidence interval.The easiest way to do this is to:

Accepted Answer

A)  decrease the confidence level in the analysis. 
B)  increase the confidence level in the analysis. 
C)  decrease the sample size. 
D)  use a distribution other than the normal distribution. 
A)  decrease the confidence level in the analysis. 
B)  increase the confidence level in the analysis. 
C)  decrease the sample size. 
D)  use a distribution other than the normal distribution.

Question 11

Adult IQs are normally distributed, with a standard deviation of 15.We sample 10 adults and find   .What is a 95% confidence interval for the mean adult IQ?

Accepted Answer

A)  (65.6, 124.4) 
B)  (85.703, 104.297) 
C)  (83.967, 106.033) 
D)  (85.513, 104.487) 
A)  (65.6, 124.4) 
B)  (85.703, 104.297) 
C)  (83.967, 106.033) 
D)  (85.513, 104.487)

The chi-square distribution is:

After constructing a 95% confidence interval for a population mean μ, you decide that the interval is too wide to be of any value.To correct this problem, you need to:

To perform diagnostics on the consistency of a laboratory scale, multiple measurements are taken using a reference weight over the course of several days.The variance observed over 20 repeated measures is 248.What is a 99% confidence interval for the measurement variance of this scale?

The confidence level is the:

A random sample of 20 observations is selected from a normally distributed population.The sample variance is 12.In the 95% confidence interval for the population standard deviation, the upper limit will be:

Suppose we wish to estimate the proportion of classes skipped by seniors in a particular large class.How many samples should be drawn if we want a 90% confidence interval with a bound on the error of estimation of 3%?

In a study of typical student grade-point averages (GPAs), we sample 16 students and find an average GPA of 2.76, with a standard deviation of 0.48.Assuming the GPAs are normally distributed, what is an interval that we can be 80% certain contains the mean student GPA?

A shady operator wants to make sure the sample results are within the confidence interval.The easiest way to do this is to:

Adult IQs are normally distributed, with a standard deviation of 15.We sample 10 adults and find .What is a 95% confidence interval for the mean adult IQ?

Why Study Statistics

An Introduction to Statistics and Statistical Inference

Tables and Graphs for Summarizing Data

Numerical Summary Measures

Probability

Random Variables and Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions

Hypothesis Tests Based on a Single Sample

Confidence Intervals and Hypothesis Tests Based on Two Samples or Treatments

The Analysis of Variance

Correlation and Linear Regression

Categorical Data and Frequency Tables

Nonparametric Statistics

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Exam 9: Confidence Intervals Based on a Single Sample

The chi-square distribution is:

After constructing a 95% confidence interval for a population mean μ, you decide that the interval is too wide to be of any value.To correct this problem, you need to:

To perform diagnostics on the consistency of a laboratory scale, multiple measurements are taken using a reference weight over the course of several days.The variance observed over 20 repeated measures is 248.What is a 99% confidence interval for the measurement variance of this scale?

The confidence level is the:

A random sample of 20 observations is selected from a normally distributed population.The sample variance is 12.In the 95% confidence interval for the population standard deviation, the upper limit will be:

Suppose we wish to estimate the proportion of classes skipped by seniors in a particular large class.How many samples should be drawn if we want a 90% confidence interval with a bound on the error of estimation of 3%?

In a study of typical student grade-point averages (GPAs), we sample 16 students and find an average GPA of 2.76, with a standard deviation of 0.48.Assuming the GPAs are normally distributed, what is an interval that we can be 80% certain contains the mean student GPA?

A shady operator wants to make sure the sample results are within the confidence interval.The easiest way to do this is to:

Adult IQs are normally distributed, with a standard deviation of 15.We sample 10 adults and find .What is a 95% confidence interval for the mean adult IQ?

Why Study Statistics

An Introduction to Statistics and Statistical Inference

Tables and Graphs for Summarizing Data

Numerical Summary Measures

Probability

Random Variables and Discrete Probability Distributions

Continuous Probability Distributions

Sampling Distributions

Hypothesis Tests Based on a Single Sample

Confidence Intervals and Hypothesis Tests Based on Two Samples or Treatments

The Analysis of Variance

Correlation and Linear Regression

Categorical Data and Frequency Tables

Nonparametric Statistics

Filters