MATH302 Week 5 Test

1. Question: The population standard deviation for the height of college football players is 2.7 inches. If we want to estimate a 95% confidence interval for the population mean height of these players with a 0.65 margin of error, how many randomly selected players must be surveyed? 2. Question: The population standard deviation for the height of college basketball players is 2.9 inches. If we want to estimate a 99% confidence interval for the population mean height of these players with a 0.45 margin of error, how many randomly selected players must be surveyed? 3. Question: The population standard deviation for the height of college hockey players is 3.2 inches. If we want to estimate 95% confidence interval for the population mean height of these players with a 0.55 margin of error, how many randomly selected players must be surveyed? 4. Question: The population standard deviation for the height of college baseball players is 3.0 inches. If we want to estimate 95% confidence interval for the population mean height of these players with a 0.68 margin of error, how many randomly selected players must be surveyed? 5. Question: The population standard deviation for the height of college basketball players is 3.4 inches. If we want to estimate 99% confidence interval for the population mean height of these players with a 0.43 margin of error, how many randomly selected players must be surveyed? 6. Question: The population standard deviation for the height of college basketball players is 2.4 inches. If we want to estimate 97% confidence interval for the population mean height of these players with a 0.35 margin of error, how many randomly selected players must be surveyed? 7. Question: Suppose a marketing company wants to determine the current proportion of customers who click on ads on their smartphones. It was estimated that the current proportion of customers who click on ads on their smartphones is 0.65. How many customers should the company survey in order to be 94% confident that the margin of error is 0.22 for the confidence interval of true proportion of customers who click on ads on their smartphones? 8. Question: A survey asked people if they were aware that maintaining a healthy weight could reduce the risk of stroke. A 97% confidence interval was found using the survey results to be (0.45, 0.67). What is the correct interpretation of this interval? 9. Question: A survey asked people if they were aware that maintaining a healthy weight could reduce the risk of stroke. A 97% confidence interval was found using the survey results to be (0.45, 0.67). What is the correct interpretation of this interval? 10. Question: Suppose a marketing company computed a 96% confidence interval for the true proportion of customers who click on ads on their smartphones to be (0.59 , 0.71). Select the correct answer to interpret this interval 11. Question: A random sample of 145 people was selected and 13% of them were left handed. Find the 97% confidence interval for the proportion of left-handed people. 12. Question: Assume 50 random samples of the same sample size are taken from a population, and a 90% confidence interval is constructed from each sample. How many of the intervals would you expect to contain the true population mean? 13. Question: The percent defective for parts produced by a manufacturing process is targeted at 4%. The process is monitored daily by taking samples of sizes n = 160 units. Suppose that today's sample contains 14 defectives. Determine a 88% confidence interval for the proportion defective for the process today. Place your LOWER limit, rounded to 3 decimal places, in the first blank. For example, 0.123 would be a legitimate answer.___ Place your UPPER limit, rounded to 3 decimal places, in the second blank. 14. Question: Which confidence level would give the narrowest margin of error? 15. Question: If a sample has 20 observations and a 95% confidence estimate for µ is needed, the appropriate value of the t-multiple required is___. Place your answer, rounded to 3 decimal places, in the blank. 16. Question: A lawyer researched the average number of years served by 45 different justices on the Supreme Court. The average number of years served was 13.8 years with a standard deviation of 7.3 years. What is the 95% confidence interval estimate for the average number of years served by all Supreme Court justices? 17. Question: A random sample of college football players had an average height of 66.5 inches. Based on this sample, (64.2, 67.1) found to be a 95% confidence interval for the population mean height of college football players. Select the correct answer to interpret this interval. 18. Question: It is known that the number of hours a student sleeps per night has a normal distribution. The sleeping time in hours of a random sample of 8 students is given below. See Attached Excel for Data. 19. Question: A random sample of stock prices per share (in dollars) is shown. Find the 92% confidence interval for the mean stock price. Assume the population of stock prices is normally distributed. 20. Question: A random sample of college football players had an average height of 67.5 inches. Based on this sample, (65.9, 69.0) found to be a 92% confidence interval for the population mean height of college football players. Select the correct answer to interpret this interval.