Meaning
Defined range of acceptable deviation from a target value identifies the limits of stable performance. A variance band creates a buffer around a metric, within which fluctuations are treated as normal noise. It acts as a filter for management attention, ensuring that minor changes do not trigger unnecessary interventions.
This boundary is established based on the historical volatility of the metric and the tolerance for error in the specific process.
Tolerance Limit
Boundary of the tolerance limit defines the exact point where a fluctuation becomes a failure. The variance band uses these limits to categorize data points as either internal noise or external signals. When a measurement stays within the band, the process is considered to be under control.
When it breaks through the edge, it signals a structural change that requires immediate attention.
Signal Width
Measure of signal width shows the amount of natural variation inherent in a system. A wide variance band indicates a process with high volatility, while a narrow one suggests precision and consistency.
Correction Trigger
Function of the correction trigger is to initiate a response when the variance band is breached. This ensures that the organization only reacts to changes that are statistically relevant.
