Rethinking Process Tracking with Percentiles: A Customer-Centric Approach

In the world of process improvement and Lean Six Sigma, traditional metrics like Defects Per Million Opportunities (DPMO) and process capability indices are widely used to measure process performance. These metrics, however, often assume that data follows a normal distribution — a pattern that doesn’t always reflect how real-world processes operate.

What happens when your data doesn’t fit neatly into a predictable pattern? When you're dealing with customer expectations, which are often more complex and subjective, traditional metrics may fall short. This is where focusing on percentiles and distribution width can provide a clearer picture of how well your process is aligning with customer needs.

Why Percentiles Matter in Process Tracking

Percentiles help you measure process performance by identifying where a certain percentage of your data falls. Instead of focusing solely on averages or defects, percentiles allow you to track how well the majority of your customers are experiencing the process.

For example, in a shipping process, you might focus on the 90th percentile of delivery times. If 90% of deliveries are consistently made within 3 days, then your process is likely in good shape. Percentiles provide more relevant, customer-centric insights by focusing on the actual outcomes that matter to your customers.

Distribution Width: Tracking Variability

Tracking the width of the distribution — or the spread between percentiles (e.g., the 90th and 10th percentiles) — helps you understand how consistent your process is. A narrow distribution suggests a more consistent process, while a wide distribution indicates high variability, which could lead to dissatisfaction.

For example, if your delivery times range from 2 days to 6 days, the 90th percentile might still meet expectations, but the variability (the width between the 10th and 90th percentiles) could reveal issues that need addressing.

"Visualizing process performance with percentiles: A clear depiction of how distribution and percentiles can reveal insights into variability, consistency, and customer-centric outcomes."

Benefits of Percentiles and Distribution Width

• Customer-Centric: Percentiles focus on the outcomes that matter most to your customers, not just the average.

• Actionable Insights: Percentiles and distribution width give you specific points to target for improvement.

• Consistent Performance: Tracking percentiles ensures your process aligns consistently with customer expectations.

  
  

Conclusion: A More Accurate Way to Track Process Performance

While traditional metrics like DPMO are helpful, they don’t always capture the full story, especially when dealing with customer expectations. By focusing on percentiles and tracking distribution width, you can gain deeper insights into how well your process is performing in a way that directly impacts customer satisfaction.

Call to Action:

How do you track process performance? Have you used percentiles in your Lean Six Sigma efforts? Let us know in the comments!