1. Given the following information, determine if the given interval can be used.

A. Poppa's Pizza has a population standard deviation of 3.7 minutes for delivery times. Can you use the z-interval?

B. Ohioans Health Clinic has 417 patients out of 2000 who qualify for Medicare. Can you use the 1-Proportion z-interval?

C. State Community College has a standard deviation of 10.4 graduates, based on a sample of graduation years. Can you use the z-interval?

D. Tiffany's Tutoring has a standard deviation of 15.7 minutes for tutoring session times. Can you use the t-interval?

2. According to the National Center for Education Statistics, the population standard deviation for seniors who took the test in 2017 was 195 points. A sample of 14 states has an average score of 1099. Find a confidence interval for: a. 62 % confidence ( , ) b. 99 % confidence ( , ) c. Using your results, describe the difference between the intervals and how it is related to their confidence level.

3. According to the National Center for Education Statistics, the population standard deviation for seniors who took the test in 2017 was 195 points. A sample of 14 states has an average score of 1099. Find a confidence interval for: a. 71 % confidence ( , ) b. 84 % confidence ( , )

4. A survey of 34 college Mathematics Departments found that they offered an average of 63 sections of courses per semester (Fall and Spring), with a standard deviation of 3.4 sections. Find a confidence interval for: a. 68 % confidence ( , ) b. 90 % confidence ( , ) c. Using your results, describe the difference between the intervals and how it is related to their confidence level.

5. A survey of 115 companies found that they paid their CEO's an average of $135,000 with a standard deviation of $3,500. Find a confidence interval for: a. 96 % confidence ( , ) b. 78 % confidence ( , )

6. In a simple random sample of 600 young people, 85% had earned a high school diploma. Complete the following parts (Round all answers to 2 decimal places.)

a) Find the 95% confidence interval for the percentage of all young people who earned a high school diploma. Answer: ___% to ___% b) Suppose that in the past, 80.63% of all young people earned high school diplomas. Does the confidence interval you found in part a support or refute the claim that the percentage of young people who earn high school diplomas has increased? Explain.

which of the following below describes this answer.

• The interval does not support this claim. This is because 80.63% is in the interval.
• The interval supports this claim. This is because 80.63% is in the interval.
• The interval does not support this claim. This is because 80.63% is not in the interval, and all values are above 80.63%.
• The interval supports this claim. This is because 80.63% is not in the interval, and all values are above 80.63%.

7. Use the following sample to estimate a population mean .

56.6

60.3

72.5

64.4

54.3

31.8

65.3

71.5

104.4

56.3

Assuming the population is normally distributed, find the 95% confidence interval about the population mean. Enter your answer as an open-interval (i.e., parentheses) accurate to two decimal places. 95% C.I. =

8. We want to obtain a sample to estimate a population mean. Based on previous evidence, researchers believe the population standard deviation is approximately =58.9=58.9. We would like to be 95% confident that the estimate is within 0.1 of the true population mean. How large of a sample size is required? Round the z-score to 3 decimal places before calculating "n". " n=

9. As a small business owner, you would like to estimate the proportion of customers who purchased an item after viewing it. You would like to be 72 % confident that the estimate has a margin of error of 4 %. How many customers need to be monitored if: a. no preliminary estimate is available? b. a preliminary monitoring discovered 57 % made the purchase? NOTE: be sure to carry your z-score out to 4 decimal places before calculating "n".