Department Store’s New Billing System The manager of a department store is thinking about establishing a new billing system for the store’s credit customers. After a thorough financial analysis, she...

Department Store’s New Billing System

The manager of a department store is thinking about establishing a new billing system for the store’s credit customers. After a thorough financial analysis, she determines that the new system will be cost-effective only if the mean monthly account is more than $170. A random sample of 400 monthly accounts is drawn, for which the sample mean is $178. The manager knows that the accounts are approximately normally distributed with a standard deviation of $65. Can the manager conclude from this that the new system will be cost-effective?