If you can...

17. A business wants to estimate the true mean annual income of its customers. The business needs to be within $200 of the true mean. The business estimates the true population standard deviation is around $1,300. If the confidence level is 95%, find the required sample size in order to meet the desired accuracy. (Points: 8)



18. An automobile safety engineer wants to estimate the mean cost to repair a Chevy Corvette involved in a 30 mile per hour head-on collision. The engineer crashes 20 Corvettes and finds the mean damage is $16,300 with a standard deviation of $2,330. Find a 95% confidence interval for the true mean cost to repair this type of car. (Points: 9)



19. An auditor wants to estimate what proportion of a bank’s commercial loan files are incomplete. The auditor randomly samples 80 files and finds 12 are incomplete. Using a 95% confidence interval, estimate the true proportion of incomplete files for ALL the bank’s commercial loans. (Points: 9)



20. An auditor wants to estimate what proportion of a bank’s commercial loan files are incomplete. The auditor wants to be within 4% of the true proportion when using a 95% confidence level. How many files must the auditor sample? No estimate of the proportion is available, so use 0.5 for the population proportion. (Points: 9)

It would be MUCH appreciated... Quiz ends in 47 mins.. Just giving it a shot. TIA