Measurement system analysis is one of the most important aspects of any Lean Six Sigma project because it mathematically determines how variation in the measurement process effects the overall variation of the process being analyzed. This analysis is important because it allows you to have confidence in the data collected during the Lean Six Sigma project. Without data that truly represents the process under analysis, any solution or changes the Lean Six Sigma project identifies might not have the desired effect.
Within measurement system analysis there are two types of measurement system error, Precision and Accuracy defined as follows:
Precision - The variability of a process measured by the standard deviation or the variance.
Example: If you throw darts against a board and they all land around the same space then you are considered precise.
Accuracy - The difference between the measured values against the actual value. Example: If you are throwing darts against a dartboard and the darts land all around the bulls eye then you are considered accurate.
The following diagram represents the breakdown of measurement system error that measurement system analysis will identify.