Attribute Charts

c-Chart vs u-Chart: Picking the Right Attribute Chart for Defect Counts

c-chart vs u-chart: when each attribute chart fits, constant vs variable inspection units, 3-sigma Poisson control limits, and a clear verdict.

control chartscomparisonattribute charts

August 7, 2026

p-Chart Control Limits: Variable Sample Size, 3-Sigma Formulas, and Laney p-Prime

Step-by-step calculation of p-chart control limits with a worked PCB inspection example. Covers the variable sample size problem (exact, average-n, and standardized approaches), the np>=5 minimum, and the Laney p-prime chart for overdispersion.

control chartsworked exampleattribute charts

April 15, 2026