My colleagues and I user JMP's Statistical Quality Control features extensively. We recently encountered a scenario where it is desirable to supply historically generated summary statistics (i.e., proportion [p] or mean [lambda]) when creating NP and C charts within Control Chart Builder. This would permit users to document long-term estimates for 'p' or 'lambda' in an approved report and continue to dynamically calculate control charts for new monitoring periods with varying sample size 'n'.
When using Control Chart Builder to produce Attributes control charts with varying sample size (n), it would be desirable to supply historically derived values for the Binomial proportion (p) or the Poisson mean (lambda). For the P chart this can already be achieved by selecting "Limits" > "Set Control Limits" > "Avg." This cannot be done, however, for the NP chart, as both the center lines and control limits will vary with sample size 'n'. Similarly, for U charts this can already be done by specifying the "Avg" as a manually set limit. This cannot be done, however, for the C chart, since both the center lines and control limits will again vary with sample size 'n'.