PPK (Process Performance Index) is a statistical indicator that measures how well a process is performing in relation to its specifications, considering real and current data, regardless of whether the process is under statistical control or not.
Unlike CPK, which assesses the theoretical capacity of the process, PPK measures the actual performance based on the results obtained during a defined period.
If the PPK is low, the process delivers results outside the expected range — even if, theoretically, it is capable (high CPK).
📊 PPK Formula
- LSL / USL: lower and upper specification limits
- x̄: mean of the measured results
- σ: actual sample standard deviation
🧩 Difference between CPK and PPK
| Factor | CPK | PPK |
|---|---|---|
| Statistical basis | Assumes statistical control (stable) | Uses real data (includes variation) |
| When to use | To validate process capability | To assess current real performance |
| Interpretation | Ideal for well-controlled process | Ideal for immediate feedback |
🔧 How AJOLLY Testing applies PPK in industrial tests
AJOLLY Testing integrates PPK calculation and analysis directly into test systems to validate stability, accuracy, and repeatability of measurements.
🧪 Measurements with traceability
- Automatic extraction of measurements by DUT, batch, or station
- PPK calculation by parameter (voltage, current, time, etc.)
- Comparison of PPK between shifts, operators, or firmware versions
📈 Real-time analysis
- Dashboards with histogram, standard deviation, mean, and trend
- Alert for parameters with PPK below 1.33 (typical quality limit)
- Correlation with top failures and FPY
📄 Performance reports
- Documentation for ISO/IATF audits with statistical attachments
- Support for the release of new products (NPI) with real data
- Basis for corrective actions (CAPA) and process adjustments
🎯 Benefits of using PPK
- Real monitoring of process stability
- Early identification of deviations and failure trends
- Reduction of rework, manual adjustments, and uncertainties
- Support for technical decision-making with real statistical data
With AJOLLY Testing, PPK is not just a number: it is an integrated tool in test and quality engineering, ensuring decisions based on real and traceable data.