Variability Reduction:

To achieve just-in-time material movement, managers reduce variability caused by both internal and external factors in the process. Variability is any deviation in the standard process to delivers perfect product on time, every time. Reducing inventory, less waste in the system will ultimately reduce uncertainty. Most variability is caused by tolerating waste or by poor inventory management or ineffective process. Variability occurs because:

1. Employees. machines, and suppliers produce units that do not conform to standards, 
2. Engineering drawings or specifications are inaccurate. It is rare event although.
3. Customer’s exact demands are unknown and improper design.

Variability can often go unseen when inventory exists. JIT philosophy is aligned with continual improvement by reducing such variability. The removal of variability allows us to move materials just-in-time for use. J1T implementation can reduce throughput time in a supply chain.
Quality improves as uncertainty decreases and variability reduces.