QETPP cheat sheet
QETPP · Keep the key ideas within reach.
Provisional: Quality Engineering & Testing Fundamentals
PDCA cycle: Plan (set objectives), Do (implement), Check (measure results), Act (standardize or correct); repeat for continual improvement.
Six Sigma DMAIC phases: Define, Measure, Analyze, Improve, Control; used for improving existing processes.
Cp = (USL - LSL) / (6σ); Cpk = min[(USL - μ)/(3σ), (μ - LSL)/(3σ)]; process must be in statistical control before capability indices are valid.
Control chart selection: X-bar/R for subgroup means and ranges (variables); p-chart for proportion defective; c-chart for defect counts per unit.
FMEA Risk Priority Number (RPN) = Severity × Occurrence × Detection; each rated 1-10; higher RPN indicates higher priority for action.
MSA GR&R % = (GR&R variation / total variation) × 100; <10% acceptable, 10-30% marginal, >30% unacceptable (AIAG guideline).
8D problem-solving steps: D1 team, D2 problem description, D3 containment, D4 root cause, D5 corrective action, D6 implementation, D7 prevention, D8 recognition.
Sampling plan terms: AQL = acceptable quality level (producer's reference); LTPD = lot tolerance percent defective (consumer's reference); OC curve plots probability of acceptance vs. lot quality.