Rolled Throughput Yield (RTY) is a critical metric in Lean Six Sigma that measures the probability of a process producing a defect-free unit through all process steps. It provides a more accurate picture of process performance than traditional yield measurements by accounting for hidden factory los…Rolled Throughput Yield (RTY) is a critical metric in Lean Six Sigma that measures the probability of a process producing a defect-free unit through all process steps. It provides a more accurate picture of process performance than traditional yield measurements by accounting for hidden factory losses and rework that occur at each stage of a multi-step process. RTY is calculated by multiplying the First Pass Yield (FPY) of each individual process step together. First Pass Yield represents the percentage of units that pass through a particular step correctly on the first attempt, before any rework or corrections are made. The formula is: RTY = FPY1 × FPY2 × FPY3 × ... × FPYn. For example, if a process has three steps with yields of 95%, 90%, and 92% respectively, the RTY would be 0.95 × 0.90 × 0.92 = 0.7866 or 78.66%. This reveals that only about 79% of products make it through the entire process correctly on the first pass. During the Define Phase of DMAIC, RTY serves as an essential baseline metric that helps project teams understand the true capability of their processes. It exposes inefficiencies that final yield metrics might mask, since products can be reworked multiple times before reaching acceptable quality levels. By establishing RTY at the project outset, teams can set realistic improvement targets and later measure the impact of their solutions. RTY also helps prioritize improvement efforts by identifying which process steps contribute most significantly to overall yield loss. Understanding RTY enables organizations to reduce hidden costs associated with rework, scrap, and inspection while improving customer satisfaction through higher quality outputs. It aligns with the Lean Six Sigma philosophy of eliminating waste and variation throughout the value stream.
Rolled Throughput Yield (RTY) - Complete Guide for Six Sigma Green Belt
What is Rolled Throughput Yield (RTY)?
Rolled Throughput Yield (RTY) is a probability-based metric that measures the likelihood that a unit will pass through an entire multi-step process with zero defects. Unlike traditional yield measurements that only consider final output, RTY accounts for hidden factory losses by multiplying the first-pass yields of each individual process step.
Why is RTY Important?
RTY is crucial for Six Sigma practitioners because it:
• Reveals hidden inefficiencies - Traditional yield metrics can mask rework and scrap occurring at intermediate steps • Provides true process capability - Shows the actual probability of producing a defect-free product • Identifies improvement opportunities - Highlights which process steps contribute most to quality losses • Supports accurate cost analysis - Helps quantify the true cost of poor quality including rework • Enables better decision-making - Offers a more realistic view of process performance
How RTY Works - The Formula
RTY is calculated by multiplying the first-pass yield (FPY) of each process step:
RTY = FPY₁ × FPY₂ × FPY₃ × ... × FPYₙ
Where FPY for each step = (Units entering step - Defects at step) / Units entering step
Alternatively: FPY = e^(-DPU) where DPU is Defects Per Unit
Example Calculation:
A process has 4 steps with the following first-pass yields: • Step 1: 95% (0.95) • Step 2: 98% (0.98) • Step 3: 92% (0.92) • Step 4: 97% (0.97)
RTY = 0.95 × 0.98 × 0.92 × 0.97 = 0.831 or 83.1%
This means only 83.1% of units pass through all steps defect-free on the first attempt.
RTY vs. Final Yield
Final Yield only measures output at the end, potentially showing 99% if defects are reworked. RTY reveals the true first-pass performance, exposing hidden quality costs.
Exam Tips: Answering Questions on Rolled Throughput Yield (RTY)
1. Memorize the multiplication principle Remember that RTY always involves multiplying yields together, not adding or averaging them.
2. Convert percentages to decimals Before calculating, convert all percentage yields to decimal form (e.g., 95% = 0.95).
3. Understand the relationship with DPU Know that RTY = e^(-Total DPU) when using the Poisson-based approach.
4. Recognize that RTY is always lower RTY will always be equal to or lower than the lowest individual step yield. If your answer is higher than any single step, recalculate.
5. Watch for trick questions Questions may provide final yield data and ask you to identify why RTY differs - the answer relates to rework and hidden factory losses.
6. Practice unit tracking Some questions require you to calculate FPY for each step before computing RTY. Track units carefully through each process step.
7. Know when to apply RTY RTY is most appropriate for serial processes where a unit must pass through multiple sequential steps.
8. Check your decimal places Small rounding errors compound when multiplying multiple yields. Maintain precision throughout your calculations.
Common Exam Question Types: • Calculate RTY given individual step yields • Determine which step has the greatest impact on RTY • Compare RTY to traditional yield metrics • Interpret what RTY values mean for process improvement priorities