Manufacturing Stuff Incorporated MSI produces plastic compon

Manufacturing Stuff Incorporated (MSI) produces plastic components for the automobile industry. Previous experience shows the mean component diameter to be 52 and the standard deviation in component diameter to be 3.74. The business owner has implemented process changes intended to reduce the mean diameter but is concerned that it may have increased the standard deviation in diameter. To evaluate the situation, the owner takes a random sample of twelve plastic components made using the modified process and measures the diameter.

In order to answer problems 1 and 2, do I need to use an upper confidence limit, lower confidence limit, or just a confidence limit of .95?

Solution

For problem 1, use lower confidence limit because the business owner wants to know that the mean diameter has been reduced from 52 or l ? 52

For problem 2, use upper confidence limit because the business owner wants to know that thestandard deviation in diameter has increased from 3.74 or u ? 3.74