Statistics process control questions?

What are the grand mean, the UCL and the LCL of a control chart for the mean?Statistics process control questions?
Basically the ';grand mean'; is where your target lies. The UCL and LCL are the ';upper control limit'; and ';lower control limit';. They are set by the sigma value that you need to attain. the greater the sigma value the further away the UCL and LCL will be relative to the mean.