Shewhart individuals control chart
From Wikipedia, the free encyclopedia
In statistical process control, the individual/moving-range chart is a control chart for variables data that uses individual measurements of a quality characteristic.
When to Use?
- In situations where opportunities to obtain data are limited, such as low production volume or testing.
- Sampling sizes greater than 1 simply do not apply, such as when sampling form homogeneous batches (eg., heat treating), or when samples have very small short-term variation. (e.g., sheet metal stamping), or for business processes (e.g., performance measures).
Why do we USE?
- To display and manage variation in process output over time.
- To identify when a process changes.
- To provide a basis for improvement.
- To distinguish special from common causes of variation ( that is, when to correct sporadic problems or when to change the process).
- To help assign causes of variation.
