1. Elementary Statistics:
Active Learning Lecture Slides
For use with Classroom Response Systems
Chapter 6: Confidence Intervals
Elementary Statistics:
Picturing the World
Fourth Edition
by Larson and Farber
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

2. Find a point estimate for the mean price of all textbooks.
A random sample of 42 textbooks has a mean price of $ and a standard deviation of $12.30.
Find a point estimate for the mean price of all textbooks.
$42
$12.30
$114.50
$2.73
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

3. Find a point estimate for the mean price of all textbooks.
A random sample of 42 textbooks has a mean price of $ and a standard deviation of $12.30.
Find a point estimate for the mean price of all textbooks.
$42
$12.30
$114.50
$2.73
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

4. Find the critical value zc necessary to form a 98% confidence interval.
2.33
2.05
0.5040
0.8365
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

5. Find the critical value zc necessary to form a 98% confidence interval.
2.33
2.05
0.5040
0.8365
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

6. Find a 98% confidence interval for the mean price of all textbooks.
A random sample of 42 textbooks has a mean price of $ and a standard deviation of $12.30.
Find a 98% confidence interval for the mean price of all textbooks.
(111.38, )
(110.08, )
(110.78, )
(109.61, )
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

7. Find a 98% confidence interval for the mean price of all textbooks.
A random sample of 42 textbooks has a mean price of $ and a standard deviation of $12.30.
Find a 98% confidence interval for the mean price of all textbooks.
(111.38, )
(110.08, )
(110.78, )
(109.61, )
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

8. Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 year. Assume the standard deviation is 4.8 years. 18 19
354
355
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

9. Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 year. Assume the standard deviation is 4.8 years. 18 19
354
355
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

10. Find the critical value tc necessary to form a 95% confidence interval with a sample size of 15.
1.960
2.145
2.131
2.120
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

11. Find the critical value tc necessary to form a 95% confidence interval with a sample size of 15.
1.960
2.145
2.131
2.120
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

12. Find a 95% confidence interval for the mean price of all DVD players.
A random sample of 15 DVD players has a mean price of $64.30 and a standard deviation of $5.60.
Find a 95% confidence interval for the mean price of all DVD players.
(61.20, 67.40)
(61.47, 67.13)
(61.22, 67.38)
(61.10, 67.51)
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

13. Find a 95% confidence interval for the mean price of all DVD players.
A random sample of 15 DVD players has a mean price of $64.30 and a standard deviation of $5.60.
Find a 95% confidence interval for the mean price of all DVD players.
(61.20, 67.40)
(61.47, 67.13)
(61.22, 67.38)
(61.10, 67.51)
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

14. In a survey of 250 Internet users, 195 have high-speed Internet access at home.
Find a point estimate for the proportion of all Internet users who have high-speed Internet access at home.
1.28
0.78
0.22
195
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

15. In a survey of 250 Internet users, 195 have high-speed Internet access at home.
Find a point estimate for the proportion of all Internet users who have high-speed Internet access at home.
1.28
0.78
0.22
195
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

16. In a survey of 250 Internet users, 195 have high-speed Internet access at home.
Find a 90% confidence interval for the proportion of all Internet users who have high-speed Internet access at home.
(1.19, 1.38)
(0.728, 0.832)
(0.731, 0.829)
(0.737, 0.823)
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

17. In a survey of 250 Internet users, 195 have high-speed Internet access at home.
Find a 90% confidence interval for the proportion of all Internet users who have high-speed Internet access at home.
(1.19, 1.38)
(0.728, 0.832)
(0.731, 0.829)
(0.737, 0.823)
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

18. You want to estimate, with 95% confidence, the proportion of households with pets. Your estimate must be accurate within 3% of the population proportion. No preliminary estimate is available. Find the minimum sample size needed.
1141
3267
1068
1067
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

19. You want to estimate, with 95% confidence, the proportion of households with pets. Your estimate must be accurate within 3% of the population proportion. No preliminary estimate is available. Find the minimum sample size needed.
1141
3267
1068
1067
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

20. Find the critical values and for a 98% confidence interval when the sample size is 25.
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

21. Find the critical values and for a 98% confidence interval when the sample size is 25.
Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley