A manufacturing firm currently receives supplies of raw materials from Supplier A. They have recently been approached by Supplier B, who has offered a more timely service. In order to investigate this claim, the firm has agreed to accept deliveries from Supplier B for a trial period in addition to those provided by Supplier A. The two suppliers have similar costs, so the firm will continue to use Supplier A unless they have significant evidence that the mean deliver y time for Supplier B is lower