First Time Yield (FTY) is a critical metric in Lean Six Sigma that measures the percentage of units or transactions that pass through a process step correctly on the initial attempt, requiring no rework, repair, or reprocessing. This metric provides valuable insight into process efficiency and qual…First Time Yield (FTY) is a critical metric in Lean Six Sigma that measures the percentage of units or transactions that pass through a process step correctly on the initial attempt, requiring no rework, repair, or reprocessing. This metric provides valuable insight into process efficiency and quality performance during the Define Phase of a DMAIC project.
FTY is calculated using a straightforward formula: FTY = (Number of Good Units Produced) / (Total Number of Units Started) × 100. For example, if a process begins with 100 units and 85 pass through successfully on the first attempt, the FTY would be 85%.
During the Define Phase, understanding FTY helps project teams establish baseline performance measurements and identify improvement opportunities. It serves as a key indicator of hidden factory costs, which represent the resources consumed when products or services must be corrected or repeated.
FTY differs from traditional yield calculations because it captures defects at each individual process step rather than only measuring final output quality. This distinction is crucial because a product might ultimately pass final inspection after multiple corrections, masking the true inefficiency within the process.
When analyzing multi-step processes, teams often calculate Rolled Throughput Yield (RTY), which multiplies the FTY of each sequential step together. This provides a more comprehensive view of overall process capability.
The benefits of tracking FTY include enhanced visibility into process performance, identification of bottlenecks and problem areas, better resource allocation decisions, and more accurate cost estimation for quality-related issues.
In the Define Phase specifically, FTY data helps teams create compelling business cases for improvement projects, set realistic project goals, and prioritize which processes need attention. By establishing accurate FTY baselines early in a project, Green Belt practitioners can later demonstrate measurable improvements and validate the success of their Six Sigma initiatives.
First Time Yield (FTY) - Complete Guide for Six Sigma Green Belt
What is First Time Yield (FTY)?
First Time Yield (FTY) is a quality metric that measures the percentage of units that pass through a process step correctly on the first attempt, with no rework, scrap, or defects. It represents the probability that a unit will be produced correctly the first time through a single process step.
The FTY Formula:
FTY = (Number of Good Units Produced) / (Total Number of Units Started)
Or alternatively:
FTY = (Units Entering Process - Defective Units - Reworked Units) / Units Entering Process
Why is First Time Yield Important?
1. True Process Performance: FTY reveals the actual capability of a process by excluding units that required correction or rework.
2. Hidden Factory Identification: It exposes the hidden costs associated with rework, inspection, and correction activities that traditional yield metrics might mask.
3. Cost Reduction: Understanding FTY helps identify where resources are being wasted on fixing problems rather than producing quality output.
4. Customer Satisfaction: Higher FTY correlates with better product quality delivered to customers.
5. Foundation for RTY: FTY values from individual process steps are multiplied together to calculate Rolled Throughput Yield (RTY).
How First Time Yield Works
Example Calculation:
A manufacturing process starts with 100 units. At the end of the process step: - 85 units passed inspection on the first attempt - 10 units required rework (and eventually passed) - 5 units were scrapped
FTY = 85 / 100 = 0.85 or 85%
Note that even though 95 units eventually passed (85 good + 10 reworked), the FTY is only 85% because it only counts units that were correct the first time.
FTY vs. Traditional Yield
Traditional Yield would count the 10 reworked units as good, showing 95% yield. FTY provides a more honest assessment at 85%, revealing the true process capability.
Key Concepts to Remember:
- FTY is always measured at a single process step - Reworked units are counted as defective for FTY purposes - FTY values are typically expressed as decimals or percentages - Multiple FTY values multiplied together give RTY
Exam Tips: Answering Questions on First Time Yield (FTY)
1. Read Carefully for Rework: Always check if the question mentions reworked units. These must be subtracted from good units when calculating FTY, even if they eventually passed.
2. Distinguish FTY from Final Yield: If a question asks specifically for FTY, do not include reworked units in your numerator. Final yield includes rework; FTY does not.
3. Watch the Starting Number: The denominator is always the number of units that entered the process step, not the number that exited.
4. Express Answers Correctly: Know whether the question wants a decimal (0.85) or percentage (85%). Convert appropriately.
5. Connect to RTY: Questions may ask you to calculate RTY using individual FTY values. Remember: RTY = FTY1 × FTY2 × FTY3...
6. Understand the Purpose: Be prepared to explain why FTY is preferred over traditional yield metrics - it exposes hidden factory waste.
7. Check Units: Ensure all values in your calculation use the same units and come from the same process step.
8. Scrap Handling: Scrapped units reduce both the numerator and are already excluded from good units. Do not double-count them.
9. Practice Word Problems: Many exam questions present scenarios where you must identify which numbers represent starting units, good units, rework, and scrap before calculating.