Statistical charts and diagrams
Shewhart individuals control chart
In statistical quality control, the individual/moving-range chart is a type of control chart used to monitor variables data from a business or industrial process for which it is impractical to use rational subgroups. The chart is necessary in the following situations: 1. * Where automation allows inspection of each unit, so rational subgrouping has less benefit. 2. * Where production is slow so that waiting for enough samples to make a rational subgroup unacceptably delays monitoring 3. * For processes that produce homogeneous batches (e.g., chemical) where repeat measurements vary primarily because of measurement error The "chart" actually consists of a pair of charts: one, the individuals chart, displays the individual measured values; the other, the moving range chart, displays the difference from one point to the next. As with other control charts, these two charts enable the user to monitor a process for shifts in the process that alter the mean or variance of the measured statistic. (Wikipedia).
