• IthinkIdidthesecorrectly,butIwantedtocheck. The4partquestionislistedbelow.Otherneededinformationis:
• SampleMean=18.11
• Samplesize=65
• PopulationSize=7823
• StandardDeviation=4.2
• 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?