2. A) Stout Electric Company operates a fleet of trucks that provide electrical service to the construction industry. Monthly mean maintenance cost has been $75 per truck with a standard deviation of $30. A random sample of 40 trucks shows a sample mean maintenance cost of $82 per month. Management wants a test to determine if mean monthly maintenance cost has decreasedso they can adjust next year budget (use a .05 level of statistical significance).

What is the test statistic you need to use in this test?

t-calc

z-calc