b What percent of customers at the drive through lane will take between 1 to 3

# B what percent of customers at the drive through lane

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b. What percent of customers at the drive-through lane will take between 1 to 3 minutes to service? Part B1. A simple random sample of 50 customers is selected from an account receivable portfolio and the sample mean account balance is \$1000. The population standard deviation s is known to be \$200. (8 points) a. Construct a 95% confidence interval for the mean account balance of the popula-tion. b. What is the margin of error for estimating the mean account balance at the 95% confidence level? c. Construct a 95% confidence interval for the mean account balance of the popula-tion if the samples mean account balance is obtained from a random sample of 100 instead of 50. Assignment #3 May 19 d. Based on the results from a. and c., what can you say about the effect of a larger sample size on the length of the confidence interval at the same confidence level? 2. A simple random sample of 50 calls is monitored at an in-bound call center and the average length of the calls is 6 minutes. The population standard deviation is unknown. Instead the sample standard deviation s is also calculated from the sam-ple and is found to be 4 minutes. (6 points) a. Construct a 99% confidence interval (using the t-distribution) for the average length of inbound calls.  • • • 