What are the Usage of Capability Studies

Capability studies are most often used to determine whether the process can meet specifications or how many parts will exceed specifications. However, there are numerous other practical uses for capability studies, including the following:

• Estimating percentage of defective parts to be expected
• Evaluating new equipment purchases
• Predicting whether design tolerances can be met
• Assigning equipment to production
• Planning process control checks
• Analyzing the interrelationships of sequential processes
• Making adjustments during manufacture
• Setting specifications
• Costing out contracts

Since a capability study determines the inherent reproducibility of parts created in a process, it can be applied to problems outside the scope of manufacturing, such as inspection, administration, and engineering.

There are instances where capability measurements are valuable even when it is not practical to determine in advance if the process is in control. Such an analysis is called a performance study.

Why Performance Studies Can Be Useful

Performance studies can be useful for examining incoming lots of materials or one-time-only production runs. In the case of an incoming lot, a performance study cannot tell us if the process that produced the material is in control; but it may tell us, by the shape of the distribution, what percent of the parts are out of specification or whether the distribution was truncated by the vendor sorting out the obvious bad parts.