Variable Charts

All variable charts have two graphs on which the data are plotted, one of which monitors location (how close each subgroup is to the process average), while the other monitors dispersion (the amount of variation within successive subgroups). The names of the major variable charts reflect the particular statistics plotted on each of these two graphs. You will often find them referred to by their shorthand names (given in brackets in the list below). The most commonly used are:

Later in this course, we will be looking in greater detail at the mean & range and the individual & moving range charts.