Statistics for Six Sigma Green Belts with Minitab and JMP

11.9. Individual Value and Moving Range Charts

Often, you are only able to measure a single value per subgroup. Perhaps measurements must be taken at relatively long intervals, or the measurements are destructive and/or expensive; or perhaps they represent a single batch where only one measurement is appropriate, such as the total yield of a homogeneous chemical batch process; or the measurements may be monthly or quarterly revenue or cost data. Whatever the case, there are circumstances when data must be taken as individual units that cannot be conveniently divided into subgroups.

Individual value charts have two parts, one that charts the process variability and the other that charts the process average. The two parts are used in tandem, as ...