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Quality knowledge base - article QA-0038
Updated on 05-01-2017

Internal Reject Rate (IRR)

In quality management IRR stands for Internal Reject Rate, which reflects the cumulative rejection rate of a given process chain (sum of sub-processes).
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Key Features
IRR is the product of individual rejection rates (fall-off-rates) of all process steps in the production chain (including manufacturing stations and test gates as well). Practically, we can state that IRR and the Rolled Fist Pass Yield add up to 100%.
IRR + Rolled FPY = 100%
To calculate IRR, we have to use the individual reject rates of our processes (or their counter-part: the individual FPY of each process).
IRR = 100% - [ (100% - Reject rate 1) * (100 - Reject rate 2) * (100 - Reject rate 3) ]
IRR = 100% - [ FPY1 * FPY2 * FPY3 ]
IRR = 100% - Rolled FPY
Example: our 3 processes generate 2%, 9.09% and 6.31% reject rates, taking both scrap and rework into account.
IRR = 100% - [ (100% - 2%) * (100% - 9.09%) * (100% - 6.31%) ]
IRR = 100% - [ 98% * 90.91% * 93.69% ]
IRR = 100% - 83.47% = 16.53%
Quality Management
Calculation of IRR (Source:
Concentrate on all process steps, not just the final test results. Based on the previous example, if a quality manager checks only the end of line test result, he sees a much better image, instead of seeing the whole process results (6.31% reject rate vs 16.53% IRR).
IRR is in close conjunction with yield metrics, such as:
  • FTY (first time yield): only calculates with input and output quantities of a process step, and does not take rework into account.
  • FPY (first pass yield) or TPY (throughput yield): takes rework into account.
  • RTY (rolled throughput yield): the product of TPY of all processes in the production chain. It is the overall throughput yield that takes rework and all defect scenarios into account.
Such as RTY, IRR also handles reworked pieces as rejected, so it is highly recommended to be used as input for process improvement.
  • IRR stands for Internal Reject Rate.
  • IRR reflects the cumulative rejection rate of a given process chain (including sub-processes, test gates, etc.).
  • IRR is in close conjunction with yield metrics, especially with rolled FPY (first pass yield).
Relevant Topics
Process Control and Analysis
Measurement System Analysis (MSA)
Process Control and Analysis
Statistical Process Control (SPC)
Process Control and Analysis
Machine- and Process Capability
Process Control and Analysis
Overall Equipment Effectiveness (OEE)
Process Control and Analysis
Incoming Quality Inspection
Process Control and Analysis
Controlled Shipping Level (CSL)
Process Control and Analysis
End of Line Test (EOL)
Fact sheet
Information about the rate of internal rejects in a production chain.

Topic / Article: Internal Reject Rate (IRR)
Term Category: Process Control and Analysis
Business Sector: All
Timing: In serial production
Files, Attachments: None
Term Up-to-date
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