Use Capability Analysis (Between/Within) to assess the capability of an in-control process when the variation in the data has both within-subgroup and between-subgroup components. A capable process is able to produce products or services that meet specifications.

For example, a process for coating paper with a thin film may have both between-subgroup and within-subgroup variation. The within-subgroup variation in the variation is film thickness within one roll (subgroup). If the machine is reset for each roll, then there might be variation between rolls (subgroups).

The process must be in control before you assess capability. If the process is not in control, then the estimates of capability will be incorrect.

Capability analysis for between-subgroup and within-subgroup variation consists of a capability histogram and a table of capability statistics.

A manufacturing process coats large rolls of paper with a thin film. Three measurements of coating thickness are taken from 25 consecutive rolls. The machine is reset for each new roll, so in addition to the variation within a roll there is a significant source of variation between rolls. The film thickness must be 50 + 3 microns to meet engineering specifications.

Data: Film.MTW (available in the Sample Data folder).