Given the Following Process Control Data for a Normally Distributed

Short Answer

Given the following process control data for a normally distributed quality variable (three samples of size four each):
If the process is known to have a mean of 15 and a standard deviation of 3,what is the alpha risk (probability of Type I error)for upper and lower control limits of 16.5 and 13.5 respectively? 18 and 12? 19.5 and 10.5?