The NPControlLimits command computes the upper and lower control limits for the NP chart. Unless explicitly given, the standard deviation of the underlying quality characteristic is computed based on the data.

The first parameter X is a single data sample, given as a Vector or list. Each value represents the number of nonconforming items in the corresponding sample.

The second parameter n specifies the size of the individual samples. All samples are expected to be of size n.

All computations involving data are performed in floating-point; therefore, all data provided must have type realcons and all returned solutions are floating-point, even if the problem is specified with exact values.

For more information about computation in the ProcessControl package, see the ProcessControl help page.

The options argument can contain one or more of the following options.

confidencelevel=realcons -- This option specifies the required confidence level. The default value is 0.9973, corresponding to a 3 sigma confidence level.

pbar=deduce or realcons -- This option specifies the average fraction of nonconforming items per data sample.

$\mathrm{with}\left(\mathrm{ProcessControl}\right)\:$

$\mathrm{infolevel}\left[\mathrm{ProcessControl}\right]≔1\:$

$A≔\left[12\,8\,6\,9\,10\,12\,11\,16\,10\,6\,20\,15\,9\,8\,6\,8\,10\,7\,5\,8\,5\,8\,10\,6\,9\right]$

$A≔\left[12\,8\,6\,9\,10\,12\,11\,16\,10\,6\,20\,15\,9\,8\,6\,8\,10\,7\,5\,8\,5\,8\,10\,6\,9\right]$

$\mathrm{NPControlLimits}\left(A\,100\right)$

$\left[0.621857384815469\,18.0981426151846\right]$

$\mathrm{NPControlLimits}\left(A\,100\,\mathrm{confidencelevel}=0.95\right)$

$\left[3.65118507466331\,15.0688149253367\right]$

Montgomery, Douglas C. Introduction to Statistical Quality Control. 2nd ed. New York: John Wiley & Sons, 1991.