In: Statistics and Probability
The director of manufacturing at a fabric mill needs to determine whether a new machine is producing a particular type of cloth according to the manufacturer’s specifications, which indicate that the cloth should have a mean breaking strength of 30 kg and a standard deviation of 3.5 kg. A sample of 49 pieces of cloth reveals a sample mean breaking strength of 29.3 kg.
(a) Is there evidence that the machine is not meeting the manufacturer’s specification for mean breaking strength? Assume that the specification of a standard deviation of 3.5 kg is being met and use a 5% level of significance.
(b) What is your answer in part (a) if the standard deviation is 1.8 kg?
(c) What is your answer in part (a) if the sample mean is 29 kg and the standard deviation is 1.7 kg?