MSA -Measurement System Analysis

The decision to adjust a manufacturing process or not is now commonly based on measurement data. Another use of measurement data is to determine if a significant relationship exists between two or more variables. Studies that explore such relationship are called analytical studies. In general, an analytic study is one that increases knowledge about the system of causes that affect the process. Analytic studies are among the most important uses of measurement data because they lead ultimately to better understanding of processes.

The benefit of using a data based procedure is largely determined by the quality of the measurement data used. To ensure that the benefit derived from using measurement data is great enough to warrant the cost of obtaining it, attention must be focused on the quality of the data.

Much of the variation in a set of measurements is due to the interaction between the measurement system and its environment. If the interaction generates too much variation, then the quality of the data may be so low that the data are not useful. For example, a measurement system with a large amount of variation may not be appropriate for use in analyzing a manufacturing process because the measurement system’s variation may mask the variation in the manufacturing process.

Much of the work of managing a measurement system is directed at monitoring and controlling variation. Among other things, this means that emphasis must be placed on learning how the measurement system interacts with its environment so that only data of acceptable quality are generated.

Most variation is undesirable. But there are some important exceptions. For instance, if the variation is due to small changes in the characteristic being measured, then it is usually considered desirable. The more sensitive a measurement system is to that kind of change, the more desirable the system becomes because it is a more sensitive measurement system.

If the quality of the data is not acceptable, then it must be improved. This is usually accomplished by improving the measurement system, rather than by improving the data themselves.