Question: Manufacturing and Product Development A manufactured glass rod is tested for the stress required for fracture. Experiments suggest that a flame-polished rod has a higher mean fracture stress than a rod with an abraded surface. In both cases, the variance in stress is designed to be at most 324 MPa2. A random sample of 12 polished glass rods was obtained, and the fracture stress for each was measured. The sample standard deviation in fracture stress was s = 21.56. Is there any evidence to refute the manufacturer's claim? Assume the underlying distribution is normal and use a = 0.01.