np-chart control limits

Calculates basic c-chart limits for an average count of nonconformities.

Calculates the existing sigma-based Xbar limits and Xbar-R chart limits from the grand mean and average range.

Calculates basic p-chart limits from pBar and sample size without creating an SPC chart.

Calculates basic u-chart limits from uBar and sample size.

Calculates defects per million opportunities from defects, units, and opportunities per unit.

Calculates defects per million units as an auxiliary quality metric.