iSixSigma

Control Chart Wizard – np-Chart

Control Chart Suggestion

np-Chart

Control Chart Description

The np control chart are used to monitor the number of nonconforming units in samples of inspected units. A nonconforming unit is a product which fails to meet at least one specified requirement. There is a difference between a defect and defective, as there is between a nonconformity and nonconforming unit. The np-chart control chart is used with discrete/attribute defective data when the sample size is greater than 50. The sample size must be constant; this control chart is only valid if data is collected in same-size subgroups.

Control Chart Formulae

np-chart Control Chart Formulae

Control Chart Example

np Chart Control Chart Example

Additional Resources

References

Wheeler, D.J., & Chambers, D.S. (1992). Understanding Statistical Process Control. Knoxville, TN: SPC Press.

Leave a Reply