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# Assume that a sample is used to estimate a population

9. Assume that a sample is used to estimate a population proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. Round the margin of error to four decimal places.
95% confidence; the sample size is 10,000, of which 40% are successes (Points : 5)
0.0072
0.0110
0.0126
0.0096

10. Use the given degree of confidence and sample data to construct a confidence interval for the population proportion p.
n = 110, x = 55; 88% confidence (Points : 5)
0.425 < p < 0.575
0.421 < p < 0.579
0.422 < p < 0.578
0.426 < p < 0.574

11. Use the given data to find the minimum sample size required to estimate the population proportion.
Margin of error: 0.05; confidence level: 99%; from a prior study, is estimated by 0.15. (Points : 5)
17
339
407
196

12. Solve the problem. Round the point estimate to the nearest thousandth.
430 randomly selected light bulbs were tested in a laboratory, 224 lasted more than 500 hours. Find a point estimate of the proportion of all light bulbs that last more than 500 hours. (Points : 5)
0.521
0.519
0.479
0.343

13. Use the given degree of confidence and sample data to construct a confidence interval for the population proportion p.
When 319 college students are randomly selected and surveyed, it is found that 120 own a car. Find a 99% confidence interval for the true proportion of all college students who own a car. (Points : 5)
0.313 < p < 0.439
0.332 < p < 0.421
0.323 < p < 0.429
0.306 < p < 0.446

14. Solve the problem.
In a certain population, body weights are normally distributed with a mean of 152 pounds and a standard deviation of 26 pounds. How many people must be surveyed if we want to estimate the percentage who weigh more than 180 pounds? Assume that we want 96% confidence that the error is no more than 4 percentage points. (Points : 5)
657
317
501
232

15. Use the confidence level and sample data to find the margin of error E. Round your answer to the same number of decimal places as the sample mean unless otherwise noted.
College students' annual earnings: 99% confidence; n = 76, (Points : 5)
\$196
\$891
\$233
\$258

16. Use the confidence level and sample data to find a confidence interval for estimating the population mu. Round your answer to the same number of decimal places as the sample mean.
A random sample of 105 light bulbs had a mean life of 441 hours with a standard deviation of 40 hours. Construct a 90% confidence interval for the mean life, mu, of all light bulbs of this type. (Points : 5)
433 hr < mu < 449 hr
435 hr < mu < 447 hr
431 hr < mu < 451 hr
432 hr < mu < 450 hr

17. Use the given information to find the minimum sample size required to estimate an unknown population mean mu.
How many women must be randomly selected to estimate the mean weight of women in one age group. We want 90% confidence that the sample mean is within 3.7 lb of the population mean, and the population standard deviation is known to be 28 lb. (Points : 5)
221
156
153
155

18. Assume that a sample is used to estimate a population mean mu. Use the given confidence level and sample data to find the margin of error. Assume that the sample is a simple random sample and the population has a normal distribution. Round your answer to one more decimal place than the sample standard deviation.
95% confidence; n = 21; x-bar = 0.16; s = 0.16 (Points : 5)
0.085
0.068
0.063
0.073

19. Use the given degree of confidence and sample data to construct a confidence interval for the population mean mu. Assume that the population has a normal distribution.
Thirty randomly selected students took the calculus final. If the sample mean was 83 and the standard deviation was 13.5, construct a 99% confidence interval for the mean score of all students. (Points : 5)
76.21 < mu < 89.79
76.23 < mu < 89.77
76.93 < mu < 89.07
78.81 < mu < 87.19

20. Solve the problem.
Find the critical value corresponding to a sample size of 24 and a confidence level of 95 percent. (Points : 5)
35.172
13.091
11.689
38.076

Here they are ...
(9) D
(10) D
(11) B
(12) A
(13) D
(14) A
(15) (Some data seems missing here. Please check.)
(16) B
(17) D
(18) D
(19) A
(20) (Options seem to be wrong. Please check)