MATH 221 Week 5 Quiz

1. Question: (CO 4) From a random sample of 68 businesses, it is found that the mean time that employees spend on personal issues each week is 5.8 hours with a standard deviation of 0.35 hours. What is the 95% confidence interval for the amount of time spent on personal issues? 2. Question: (CO 4) If a confidence interval is given from 8.52 to 10.23 and the mean is known to be 9.375, what is the maximum error? 3. Question: (CO 4) Which of the following is most likely to lead to a small margin of error? 4. Question: (CO 4) From a random sample of 41 teens, it is found that on average they spend 31.8 hours each week online with a population standard deviation of 5.91 hours. What is the 90% confidence interval for the amount of time they spend online each week? 5. Question: (CO 4) A company making refrigerators strives for the internal temperature to have a mean of 37.5 degrees with a standard deviation of 0.6 degrees, based on samples of 100. A sample of 100 refrigerators have an average temperature of 37.70 degrees. Are the refrigerators within the 90% confidence interval? 6. Question: (CO 4) What is the 97% confidence interval for a sample of 104 soda cans that have a mean amount of 12.05 ounces and a population standard deviation of0.08 ounces? 7. Question: (CO 4) Determine the minimum sample size required when you want to be 98% confident that the sample mean is within two units of the population mean. Assume a standard deviation of 8.98 in a normally distributed population. 8. Question: (CO 4) Determine the minimum sample size required when you want to be 80% confident that the sample mean is within 1.3 units of the population mean. Assume a standard deviation of 9.24 in a normally distributed population. 9. Question: (CO 4) Determine the minimum sample size required when you want to be 75% confident that the sample mean is within thirty units of the population mean. Assume a standard deviation of 327.8 in a normally distributed population 10. Question: (CO 4) In a sample of 8 high school students, they spent an average of 25.8 hours each week doing sports with a standard deviation of 3.2 hours. Find the 95% confidence interval. 11. Question: (CO 4) In a sample of 15 stuffed animals, you find that they weigh an average of 8.56 ounces with a standard deviation of 0.07 ounces. Find the 92% confidence interval. 12. Question: (CO 4) Market research indicates that a new product has the potential to make the company an additional $3.8 million, with a standard deviation of $1.6 million. If this estimate was based on a sample of 10 customers, what would be the 90% confidence interval? 13. Question: (CO 4) Supplier claims that they are 95% confident that their products will be in the interval of 20.45 to 21.05. You take samples and find that the 95% confidence interval of what they are sending is 20.40 to 21.00. What conclusion can be made? 14. Question: (CO 4) In a sample of 18 small candles, the weight is found to be 3.72 ounces with a standard deviation of 0.963 ounces. What would be the 87% confidence interval for the size of the candles? 15. Question: (CO 4) In a situation where the standard deviation was increased from 3.1 to 5.8, what would be the impact on the confidence interval? 16. Question: (CO 4) In a random sample of fourteen people, the mean time at lunch was 35.6 minutes with a standard deviation of 8.2 minutes. Assuming the data are normally distributed, what would be the 85% confidence interval? 17. Question: (CO 4) If a confidence interval is known to be (13.67, 17.53), what would be its margin of error? 18. Question: (CO 4) A company manufacturers soda cans with a diameter of 52 millimeters. In a sample of 12 cans, the standard deviation was 2.3 millimeters. What would be the 96% confidence interval for these cans?