Review the Payment Time Case Study and Data Set.

Develop a 700-word report including the following calculations and using the information to determine whether the new billing system has reduced the mean bill payment time:

o   Assuming the standard deviation of the payment times for all payments is 4.2 days, construct a 95% confidence interval estimate to determine whether the new billing system was effective. State the interpretation of 95% confidence interval and state whether or not the billing system was effective.

o   Using the 95% confidence interval, can we be 95% confident that µ ≤ 19.5 days?

o   Compute the 99% confidence interval. Using the 99% confidence interval, can we be 99% confident that µ ≤ 19.5 days?

o   If the population mean payment time is 19.5 days, what is the probability of observing a sample mean payment time of 65 invoices less than or equal to 18.1077 days?

Format your assignment consistent with APA format. Remember to show how you computed your statistics in your paper.