In quality engineering , there are static and dynamic characteristics . We can understand the difference of them by other approaches.
Static characteristic is used to study the unevenness of Y. It is one-dimension unevenness.
Dynamic characteristic is use to study the unevenness of the relationship between Y and X. It is two-dimension unevenness.
There is a difference in the definition of SN ratio. For SN ratio of dynamic characteristics, the value of X is used to calculate SN ratio. But for static, X is not used.
For example, in System Engineering and System Dynamics , "Dynamic" means "time depended phenomena".
But, in quality engineering, the difference of static and dynamic is not related to time dependence. It is the important point to understand the quality engineering.
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