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: 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. Using the 95% confidence interval, can we be 95% confident that 19.5 days? Using the 99% confidence interval, can we be 99% confident that 19.5 days? 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? Major consulting firms such as Davis and shirtliff, Ernst & Young Consulting, and Deloitte & Touche Consulting employ statistical analysis to assess the effectiveness of the systems they design for their customers. In this case, a consulting firm has developed an electronic billing system for a Stockton, CA, trucking company. The system sends invoices electronically to each customer's computer and allows customers to easily check and correct errors. It is hoped the new billing system will substantially reduce the amount of time it takes customers to make payments. Typical payment timesmeasured from the date on an invoice to the date payment is receivedusing the trucking company's old billing system had been 39 days or more. This exceeded the industry standard payment time of 30 days. The new billing system does not automatically compute the payment time for each invoice because there is no continuing need for this information. The management consulting firm believes the new system will reduce the mean bill payment time by more than 50 percent. The mean payment time using the old billing system was approximately equal to, but no less than, 39 days. Therefore, if denotes the new mean payment time, the consulting firm believes that will be less than 19.5 days. Therefore, to assess the system's effectiveness (whether < 19.5 days), the consulting firm selects a random sample of 65 invoices from the 7,823 invoices processed during the first three months of the new system's operation. Whereas this is the first time the consulting company has installed an electronic billing system in a trucking company, the firm has installed electronic billing systems in other types of companies. Analysis of results from these other companies show, although the population mean payment time varies from company to company, the population standard deviation of payment times is the same for different companies and equals 4.2 days. The payment times for the 65 sample invoices are manually determined and are given in the Excel spreadsheet named \"The Payment Time Case\". If this sample can be used to establish that new billing system substantially reduces payment times, the consulting firm plans to market the system to other trucking firms. 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. EQUATION CI=X Z/ N Confidence Interval Estimate for the Mean Data Population Standard Deviation 4.2 Sample Mean 18.10 77 Sample Size 65 Confidence Level 95% Intermediate Calculations Standard Error of the Mean 0.520 9 Z Value 1.960 0 Interval Half Width 1.021 0 Confidence Interval Interval Lower Limit 17.08 67 Interval Upper Limit 19.12 87 Using the 95% confidence interval, can we be 95% confident that 19.5 days? 95% CI =(17.0867, 19.1287) less than 19.5. We conclude that 95% confident that 19.5 days. Using the 99% confidence interval, can we be 99% confident that 19.5 days? Confidence Interval Estimate for the Mean Data Population Standard Deviation 4.2 Sample Mean 18.10 77 Sample Size 65 Confidence Level 99% Intermediate Calculations Standard Error of the Mean 0.520 9 Z Value 2.576 0 Interval Half Width 1.341 9 Confidence Interval Interval Lower Limit 16.76 58 Interval Upper Limit 19.44 96 99% CI =(16.7658, 19.4496) less than 19.5. We conclude that 99% confident that 19.5 days. 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? Z value for 18.1077 is z =(18.107719.5)/0.5209 = 2.67 P( mean x <18.1077) = P( z < 2.67) =0.0038