3. 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. 90% confidence; n=300,x=50
4. Use the given degree of confidence and sample data to construct a confidence interval for the population proportion p. n=130, x=65; 90% confidence
5. A savings and loan association needs information concerning the checking account balances of its local customers. A random sample of 14 accounts was checked and yielded a mean balance of $664.14 and a standard deviation of $297.29. Find a 98% confidence interval for the true mean checking account balance for local customers.
6. a. Using a t-distribution to construct a confidence interval estimate for the mean of a population and solve it. 95%; n=40; standard deviation is unknown; population appears to be skewed. b. Suppose you make a mistake while solving the problem in part a and use the z-distribution. Solve the problem using the z-distribution. c. Briefly discuss the reason for the difference, or the lack of difference, between the two answers
7. When analyzing the last digits of telephone numbers in Port Jefferson, it is found that among 1000 randomly selected digits, 119 are zeros. If the digits are randomly selected, the proportion of zeros should be 0.1.
a. Use the traditional method with a 0.05 significance level to test the claim that the proportion of zeros equals 0.1.
b. Use the P-value method with a 0.05 significance level to test the claim that the proportion of zeros equals 0.1.
c. Use the sample data to construct a 95% confidence interval estimate of the proportion of zeros. What does the confidence interval suggest about the claim that the proportion of zeros equals 0.1?
d. Compare the results from the traditional method, the P-value method, and the confidence interval method. Do they all lead to the same conclusion?
8. The health of the bear population in Yellowstone National Park is monitored by periodic measurements taken from anesthetized bears. A sample of 54 bears has a mean weight of 182.9 lb.
Assuming that the standard deviation is known to be 121.8 lb, use a 0.05 significance level to test the claim that the population mean of all such bear weights is greater than 150 lb.
9. Data set 13 in appendix B lists measured voltage amounts obtained from the author's back-up UPS (APC model CS 350).