Answer to Question #51152 in Statistics and Probability for Mike S.

Question

2. A screw manufacturer makes specialized tiny screws that are 15mm long. The manufacturing process does not make every screw exactly 15mm long. If the lengths of the screws are normally distributed with population mean 15mm and population standard deviation 0.04mm. To test for quality control, 100 screws are to be measured. What is the distribution of the sample means for samples of size 100?

3. A screw manufacturer makes specialized tiny screws that are suppose to be 15mm long. The manufacturing process does not make every screw exactly 15mm long. The lengths of the screws are normally distributed with population standard deviation 0.04mm. A quality control manager thinks that the screws being made actually have mean lengths longer than 15mm. What is her null hypothesis and alternative hypothesis for testing this belief?