You may need to use the appropriate appendix table or technology to answer this question.

A simple random sample of 80 items resulted in a sample mean of 60. The population standard deviation is

= 5.

(a)Compute the 95% confidence interval for the population mean. (Round your answers to two decimal places.)

________ to _______

(b)Assume that the same sample mean was obtained from a sample of 160 items. Provide a 95% confidence interval for the population mean. (Round your answers to two decimal places.)

________ to ______

2. You may need to use the appropriate appendix table or technology to answer this question.

(a)A survey of small businesses with websites found that the average amount spent on a site was $11,000 per year with a standard deviation of $4,000. Given a sample of 40 businesses, what is the margin of error if you are to assume a 95% confidence level? (Round your answer to two decimal places.)

(b)What sample size would you recommend if the study required a margin of error of approximately $800? (Your answer should be a whole number since you can't have part of a business surveyed.)

3. You may need to use the appropriate appendix table or technology to answer this question. A 95% confidence interval for a population mean was reported to be 150.33 to 157.67. If = 15, what sample size was used in this study? (Round your answer to the nearest integer.)