- In Systems Engineering, a $10 expression referring to the number of system characteristics that can take values without regard to interactions with those taken by any other system characteristics, i.e., “independent” variables. This concept is important in System Engineering, because it is the key to limiting the number of Performance Requirements we write. Without it, we’d write requirements on every topic we can think of, and let the Verification phase sort out any implicit contradictions1. This notion should be, therefore, the proper heart of all Model-based System Engineering.
- In linear regression, the number of non-constant terms in the statistically reduced regression model. Some of these terms can involve more than one “independent” variable. For example, the expression “x+2xy+y” has three (3) DoF with only two (2) independent variables.
To really bake your noodle, the two concepts are actually the same thing, if you carefully define the word “variable”.
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