A manager has to develop a control chart for determining whether three homogenous processes are in control. Accordingly, she sampled four units of output from each process, with the following results: Process 1 - 17, 15, 15, 17 Process 2 - 16, 25, 18, 25 Process 3 - 23, 24, 23, 22 What are the x-bar chart three-sigma upper and lower control limits? Process 1 Process 2 Process 3 All processes None