ABSTRACT
The AIAG reference adds that use of separate control charts for each part is the best way to assess the status of the process. The standardized range chart or standard deviation chart can be used instead of the quantile of the chi-square statistic if this is preferred, although the control limits will then vary according to the sample size. The example in which C was running below its nominal generated points below the lower control limit and, if the characteristic was in fact a hole, our reaction plan might be to change the drill bit. The group chart's express purpose is to handle a very wide variety of part types or quality characteristics without excessive complexity. The specification width for each feature is 0.05 mm, which makes it reasonable to believe that the variation is the same for each hole, noting especially that the same machine and spindle perform the job.
