Bob is the owner of a home improvement store. He has hired you to check his machine's calibration prior to starting production on a large order. To check this, you set the machine to create 1.5 inch bolts and manufacture a random sample of 200 bolts. That sample of bolts has an average length of 1.521 inches with a standard deviation of 0.204 inches.

Does this sample provide convincing evidence that the machine is working properly or should it be shut down for repairs?