A Chinese factory produces mother-of-pearl buttons. The mean diameter of buttons is assumed to be normally distributed.If the machinery is working correctly, the mean diameter of the buttons will be 1.3cm. The variance for that machine is known to be 0.0081 cm2. A sample of 16 buttons is measured with a laser, and found to have a mean diameter of 1.25cm. Test at the 5% level of significance, the hypothesis that the mean diameter of the population differs from 1.3cm.