a manager of the credit department for an oil company would like to determine whether the mean monthly balance of credit card holders is equal to $75. an auditor selects a random sample of 100 accounts and finds that the mean owed is $83.40 with a sample standard deviation of $23.65. if you were to conduct a test to determine whether the auditor should conclude that there is evidence that the mean balance is different from $75, finish the following four questions.