RPD and SEP calculator
Free RPD and SEP calculator for NIR models: enter the reference standard deviation and SEP to get RPD, a quality band and a result you can share.
The short answerRPD = standard deviation of the reference values divided by SEP. Higher is better. Rule of thumb: 3 or more is acceptable for QC, 5 or more is excellent, under 2 is poor.
Rules of thumb as given in the course glossary: acceptable for QC at 3 or more, excellent at 5 or more, poor under 2.
How to use it
- Hold back an independent test set the model never saw.
- Compute the SD of its reference values and the SEP of the predictions.
- Divide. Report RPD together with RMSEP, never R-squared alone.
Go deeper in the course
L23
See in curriculum Introduction to Calibration
Week 6 · 18 min
L24
See in curriculum Calibration Validation Techniques
Week 6 · 19 min
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Questions
What is RPD in NIR?
RPD is the Ratio of Performance to Deviation: the standard deviation of the reference values divided by SEP. It is a scale-free way to judge whether the NIR model is doing useful work.
What RPD is good enough?
As a rule of thumb, 3 or more is acceptable for QC, 5 or more is excellent, and under 2 is poor.
Which SD do I use?
Use the standard deviation of the reference values of the independent test set, the same samples that SEP was computed on.