Computing std devs for Control Charts?
Hi. I have a question for any 6-sigma folks out there. In the Quality and Process Methods section of the User Manual, under "Statistical Details for Control Chart Builder", the standard deviation seems to be approximated using the range. For example, for XmR charts, the standard dev formula is:where MR-bar is the average of the moving range and d2 is a value from a lookup table. I'm not unfami...