Discussion:
Q: Yaschchin (1995) discusses a process for the chemical etching of silicon wafers used in itegrated circuits. This company wishes to detect an increase in the thickness of the silicon oxide layers because thicker layers require longer etching times. Process specifications state a target value of 1 micron for the true mean thickness. Historically, the layer thickness have a standard deviation of 0.06 micron.
a. A recent random sample of four wafers yielded a sample mean of 1.134. Conduct a hypothesis test to determine whether the true mean thickness has increased. Use a significance level of 0.05.
b. Find the p-value associaite with the test in part a.
c. Construct a 95% confidence interval for this situation. Use this interval to determine whether the true mean thickness has changed. Discuss the relationship of the 95% confidence interval and the corresponding hypothesis test.