DFA combines two features.
First, consumers make a forced Yes/No judgement about whether an attribute applies, followed by a short sureness rating.
Second, each attribute is examined from both sides. For example, instead of asking only whether a product is convenient to use, consumers also evaluate its negative counterpart, inconvenient to use, separately.
This structure was designed to make consumers’ judgements more consistent and to reduce response bias and variation in scale use.
Compared with a conventional one-step applicability scale, DFA provided better product discrimination, particularly during later stages of the usage experience where the simpler scale detected few or no differences.
The sureness judgement also added information beyond the initial Yes/No response, further improving discrimination.