Abstract

A significant barrier to successful lean implementation is the waste of variability. Many organizations attempt to optimize processes without first establishing consistency, leading to ineffective improvements. Variability, manifested in inconsistent inputs, outputs, and a lack of standardization undermines predictability and increases costs. We believe that variability should be recognized as a critical, “9th waste” of lean. By addressing this inconsistency, organizations can establish a stable foundation for process improvement. This paper explores how to identify and eliminate variability, enabling the transition from daily tasks performed to brilliant, repeatable processes.

Introduction

Lean manufacturing and process improvement methodologies are built upon the foundation of eliminating waste to enhance efficiency and effectiveness. The traditional seven (or eight) wastes – Transportation, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects, and sometimes Underutilized Talent – are critical targets. However, a foundational element often not explicitly emphasized in discussion of waste is variability.

Variability, the inconsistency in processes, inputs, and outputs, should not simply be an inferred aspect of lean; it is a core waste that directly undermines the principles of process stability and predictability. Many organizations attempt to optimize processes without rigorously addressing variability, leading to limited and unsustainable improvements. This is because variability is often the root cause of the traditional wastes.

Understanding Variability

Variability refers to the degree to which a process, input, or output deviates from a standard or expected value. It encompasses both natural variation, which is inherent in any process, and assignable variation, which is caused by specific factors. In the context of lean, variability is not just a symptom; it is a fundamental driver of waste. It undermines predictability, increases lead times, inflates costs, and diminishes customer satisfaction.

Taiichi Ohno’s concept of a “brilliant process” hinges on consistency and repeatability. Variability directly obstructs this vision. When tasks are executed differently each time, there is effectively no way to optimize that process to remove the non-value-added work. Consider a common business process: communication. We often find enormous variability in how information is passed between departments. An employee might send an email one day, a text message the next, and have a verbal conversation the following day, all to hand off the same task to the next business process. This variability often leads to confusion and missed information.

Recognizing Variability: Identifying the Problem

Identifying variability requires active investigation, going beyond surface-level observations, to uncover how work is truly performed. Start by interviewing those doing the work, asking open-ended questions like, “How do you do this task?” and “What different inputs do you use?” Listen for discrepancies; if team members performing the same job describe different processes, you’ve found variability. Also, look for “Dave” situations, where a process relies solely on one person’s knowledge, indicating a lack of standardization.

We frequently use SIPOC analysis (Supplier, Input, Process, Output, Customer) to visualize the process, focusing on inputs—are there multiple sources of the same input? For example, maybe some requests come via email or a tech system, while others are a phone call or water-cooler conversation. Any time there are multiple places to check for a handoff, there’s an opportunity to drop the ball in the transition.

Lean process mapping is our last key approach to identifying hidden variability. Visually mapping the different forms of inputs help to make the waste obvious. In addition, mapping makes it easier for different people in the same role to recognize they tackle the same challenges differently.

Addressing Variability: Establishing Process Stability

Addressing variability requires a systematic and explicit approach, focused on establishing foundational process stability. Standardization is paramount. Creating effective SOPs ensures that tasks are performed consistently, regardless of who is performing them. Clearly defined roles and responsibilities further enhances process stability.

Training and communication play a vital role in establishing process stability. Ensuring that all team members understand and adhere to standard processes requires comprehensive and ongoing training programs. Fostering a culture of continuous improvement explicitly encourages employees to identify and address variability proactively.

Typically, much of the variability we see comes down to not realizing there’s a better way. Either one department doesn’t see the chaos they’re causing another team, or an individual doesn’t realize there’s a better way to complete the task in front of them. Or maybe it’s just that no one bothered to take a step back and intentionally decide what the standard should be.

Whatever the cause, we find that using standard lean tools like process flow mapping can highlight variability. We label non-value-added steps with one of the 8 wastes – or variability, to keep ourselves accountable to finding a way to eliminate the problems. The resulting processes are more streamlined and efficient, while still being effective to our customer goals.

Conclusion

Eliminating variability yields numerous benefits, primarily by building a solid foundation for all other lean initiatives. Improved process efficiency and effectiveness are direct results. Reduced waste and increased throughput lead to lower costs and higher productivity. Enhanced predictability and reliability enable organizations to meet customer demands consistently and be more robust to individual employee preferences.

Ultimately, treating variability as the 9th waste of lean supports a sustainable lean transformation. Building a solid foundation for continuous improvement requires stable and predictable processes. Creating a culture of excellence, where employees are empowered to explicitly identify and eliminate waste, ensures long-term success.