The basic principles underlying UCD are:
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Based on trial and error
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More art than science
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Nonexistent, good design is just applied common sense
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Derived from empirical data regarding human performance characteristics
UCD is grounded in empirical research about human capabilities and limitations. It relies on data from usability studies, cognitive psychology, and human factors research. Options A, B, and C incorrectly dismiss the scientific foundations of UCD.
User Centered Design principles are grounded in empirical data about human performance — findings from cognitive psychology, human factors research, and usability studies about how people perceive, learn, and interact with interfaces. This evidence-based foundation is what distinguishes UCD from ad hoc design. It is not based on trial and error, is not merely 'more art than science' (though craft plays a role, UCD's core principles are research-driven), and is not simply 'applied common sense' — common sense often conflicts with what usability research actually shows about user behavior, which is precisely why formal UCD principles exist.