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...

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 . 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

The Italian Peoples Bakery in Pennington, New Jersey, advertises an original-recipe cream puff packed with 3 ounces of filling. To produce a consistent product, the variance in cream filling is carefully monitored. In a random sample of 23 cream puffs, the variance in filling was s = 5 0.105 ounce2 . Is there any evidence to suggest the variance in filling is greater than 0.09 ounce2 ? Assume normality and use