17-3. Suppose that an X chart is used to control a normally distributed process, and that samples of size n are taken every h hours and plotted on the chart, which has k sigma limits. (a) Find the expected number of samples that will be taken until a false action signal is generated. This is called the in-control average run length (ARL) (b) Suppose that the process shifts to an out-of-control state. Find the expected number of samples that will be taken until a false action is generated. This is the out-of-control ARL. (c) Evaluate the in-control ARL for k=3. How does this change if b k =2? What do you think about the use of 2-sigma limits in practice? (d) Evaluate the out-of-control ARL for a shift of one Sigma, given that n = 5.