A firm that produces one-gallon jugs of milk wants to ensure that the machine is operating properly. Every two hours, the company samples 25 jugs and calculates the following sample mean filling weights (in ounces):

128.7 128.4 128.0 127.8 127.5 126.9 Assume that when the machine is operating properly, μ = 128 and σ = 2, and that filling weights follow the normal distribution. Can the firm conclude that the machine is operating properly? Should the firm have any concerns with respect to this machine? L056