Slide 10- 1Copyright © 2010 Pearson Education, Inc.

Active Learning Lecture Slides For use with Classroom Response Systems

Business Statistics First Edition

by Sharpe, De Veaux, Velleman

Chapter 10:

Confidence Intervals for Proportions

Slide 10- 2Copyright © 2010 Pearson Education, Inc.

The higher the level of confidence we want, the narrower our confidence interval becomes.

A. True

B. False

Slide 10- 3Copyright © 2010 Pearson Education, Inc.

The higher the level of confidence we want, the narrower our confidence interval becomes.

A. True

B. False

Slide 10- 4Copyright © 2010 Pearson Education, Inc.

In constructing a confidence interval for a proportion, we add and subtract the _________ from the sample proportion.

A. margin of error

B. critical value

C. confidence level

D. standard error

Slide 10- 5Copyright © 2010 Pearson Education, Inc.

In constructing a confidence interval for a proportion, we add and subtract the _________ from the sample proportion.

A. margin of error

B. critical value

C. confidence level

D. standard error

Slide 10- 6Copyright © 2010 Pearson Education, Inc.

The Success/Failure Condition that ensures the sample size is large enough to use the Central Limit Theorem has the expectation of at least ____ “successes” and ____ “failures.”

A. 5

B. 10

C. 15

D. 25

Slide 10- 7Copyright © 2010 Pearson Education, Inc.

The Success/Failure Condition that ensures the sample size is large enough to use the Central Limit Theorem has the expectation of at least ____ “successes” and ____ “failures.”

A. 5

B. 10

C. 15

D. 25

Slide 10- 8Copyright © 2010 Pearson Education, Inc.

We have calculated a 95% confidence interval and would prefer to have a smaller margin of error without losing any confidence. In order to do this, we can

I. change the z∗ value to a smaller number.II. take a larger sample.III. take a smaller sample.

A. I only

B. II only

C. III only

D. I and II

Slide 10- 9Copyright © 2010 Pearson Education, Inc.

We have calculated a 95% confidence interval and would prefer to have a smaller margin of error without losing any confidence. In order to do this, we can

I. change the z∗ value to a smaller number.II. take a larger sample.III. take a smaller sample.

A. I only

B. II only

C. III only

D. I and II

Slide 10- 10Copyright © 2010 Pearson Education, Inc.

Which is true about a 98% confidence interval for a population proportion based on a given sample?

I. We are 98% confident that the sample proportion is in our interval.II. The interval is narrower than a 95% confidence interval.III. The interval is wider than a 95% confidence interval.

A. I only

B. II only

C. III only

D. I and II

Slide 10- 11Copyright © 2010 Pearson Education, Inc.

Which is true about a 98% confidence interval for a population proportion based on a given sample?

I. We are 98% confident that the sample proportion is in our interval.II. The interval is narrower than a 95% confidence interval.III. The interval is wider than a 95% confidence interval.

A. I only

B. II only

C. III only

D. I and II

Slide 10- 12Copyright © 2010 Pearson Education, Inc.

We have calculated a confidence interval based on a sample of size n = 100. Now we want to get a better estimate with a margin of error that is only one-fourth as large. How large does our new sample need to be?

A. 50

B. 200

C. 400

D. 1600

Slide 10- 13Copyright © 2010 Pearson Education, Inc.

We have calculated a confidence interval based on a sample of size n = 100. Now we want to get a better estimate with a margin of error that is only one-fourth as large. How large does our new sample need to be?

A. 50

B. 200

C. 400

D. 1600

Slide 10- 14Copyright © 2010 Pearson Education, Inc.

A news poll which estimated that 82% of all voters believe global warming exists had a margin of error of +/- 3%. Suppose an environmental group planning a follow-up survey on this issue wants to determine a 95% confidence interval with a margin of error of no more than 2%. How large a sample do they need?

A. 32

B. 1418

C. 999

D. 38

Slide 10- 15Copyright © 2010 Pearson Education, Inc.

A news poll which estimated that 82% of all voters believe global warming exists had a margin of error of +/- 3%. Suppose an environmental group planning a follow-up survey on this issue wants to determine a 95% confidence interval with a margin of error of no more than 2%. How large a sample do they need?

A. 32

B. 1418

C. 999

D. 38

Slide 10- 16Copyright © 2010 Pearson Education, Inc.

A large multinational corporation recently implemented an ERP system. A survey was done to determine the level of satisfaction with the new system. Out of 350 managers surveyed, 280 indicated that they were satisfied. What is the standard error for the proportion of satisfied managers?

A. 0.20

B. 0.80

C. 0.16

D. 0.02

Slide 10- 17Copyright © 2010 Pearson Education, Inc.

A large multinational corporation recently implemented an ERP system. A survey was done to determine the level of satisfaction with the new system. Out of 350 managers surveyed, 280 indicated that they were satisfied. What is the standard error for the proportion of satisfied managers?

A. 0.20

B. 0.80

C. 0.16

D. 0.02

Slide 10- 18Copyright © 2010 Pearson Education, Inc.

A large multinational corporation recently implemented an ERP system. A survey was done to determine the level of satisfaction with the new system. Out of 350 managers surveyed, 280 indicated that they were satisfied. At 95% confidence, what is the margin of error for the proportion of satisfied managers?

A. +/- 1.5680

B. +/- 0.0392

C. +/- 0.3136

D. +/- 0.0515

Slide 10- 19Copyright © 2010 Pearson Education, Inc.

A large multinational corporation recently implemented an ERP system. A survey was done to determine the level of satisfaction with the new system. Out of 350 managers surveyed, 280 indicated that they were satisfied. At 95% confidence, what is the margin of error for the proportion of satisfied managers?

A. +/- 1.5680

B. +/- 0.0392

C. +/- 0.3136

D. +/- 0.0515