# About measurement systems analysis

## What is measurement systems analysis (MSA)?

Measurement systems analysis is a method for determining whether a measurement system is acceptable. Specifically, measurement systems analysis determines how much of the total variation in a process is from the measurement system rather than from the parts that are measured.

Evaluation of your measurement system should be done before using control charts, capability analysis, or any another analysis, to prove that your measurement system is accurate and precise, and that your data are reliable.

## What is a measurement system?

Measurement systems can include all the things, such as measurement devices, measurement procedures, and operators, that affect the measurement of a part.

### Example of a measurement system

A company conducts a survey to determine how effective its internet advertisements are. In this process, the measurement system includes the order of the survey questions, the employees (operators) who conduct the surveys, the way the data from the survey is recorded, among other variation.

## What is measurement system variation?

Measurement system variation is the variation that occurs when you measure something. Specifically, measurement system variation is the sum of variation from repeatability and reproducibility.

Any component of a measurement system, such as a gage, a procedure, and software, can be a source of variation.

### Example of measurement system variation

Operators at a manufacturing company use calipers to measure the diameters of shafts. A known standard shaft has a diameter of 5 cm. When measured multiple times, the measurements are: 5.01 cm, 4.99 cm, 4.97 cm, 5.03 cm, 5.01 cm. The variation in the measurements is due to measurement system variation.

If the operators were to measure different parts that are made, are the differences due to measurement system variation or due to actual differences in the parts themselves? If the measurement system variation is large compared to part-to-part variation, the measurements may not provide useful information.

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